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„Gooi^lc
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DYNAMO, MOTOR AND
SWITCHBOARD CIRCUITS
FOR
ELECTRICAL ENGINEERS
A PRACTICAL BOOK DEALING WITH THE
~ SUBJECT OF DIRECT, ALTERNATING
AND POLYPHASE CURRENTS
WILLIAM RUSHTON BOWKER
CntnltiKg EUctrica! and Sirtcl Sailjear Engliucr, Profisuir of Pkyiics, EUctrUal
and Stnil Rai/u^r EneimiHnt fn Ihi UnivirsUj s,/ Simlkim Ca1ifir«iit, L»
Anet/es, Cal!/cn.ia.
Seconal iEtiition, Kcbiseti antr gteatls ISnlacselr.
NEW YORK
D. VAN NOSTRAND COMPANY
23 MDRRAT AND 27 WARREN STREETS
LONDON
CROSBY LOCKWOOD AND SON
1908
jvGoO'^lc
titHtaw-
v^
X-'-'
%\
Diq.izeobvGoOi^lc
PREFACE.
While there aie many excellent books dealing with the subject
of Direct, Alternating and Polyphase Currents from a Theoretical,
Mathematical and Text-book point of view, there are none, to
the Author's knowledge, dealing with these subjects in a non-
matbemattcal and practical standpoint on similar lines to those of
this book.
The title of the volume indicates clearly what information is
intended to be presented to the reader.
It is intended as a Practical Handbook for Electrical Engineers
and Artizans.
It is not intended as a Theoretical Text-book ; still, at the same
time, it will be found useful for students preparing for the City and
Guilds of London Examinations in Electrical Engineering, as it
covers certain important sections of the Syllabus of the Ordinary
and Honours Grades.
It would be practically impossible to ^ve every and all connections
and circuits applicable to these extensive branches of Electrical
En^neering ; but, in the Author's opinion, there are enougb
diagrams with explanations to generally cover the iield.
The Introductory Section of the book gives certain information
in a condensed form (which is not dealt with theoretically) as an
explanatory section, so as to make the following sections clear and
easily understood.
The Author has great pleasure in ofiering many thanks to Messrs*
A. 0. Eborall, J. K. Salter, and Ellis H. Cjapper, for kind permission
204816
„Gooi^lc
Iv PREFACE.
10 utilise extracts from articles written by them ; he has also used
as books of reference Mr. Tyson Sewell's " Elements of Electrical
Engineering" (Crosby Lockwood), his own book on "Practical
Construction of Electric Tramways" (Spon), and the excellent
weekly periodicals, the Electrical Review and Electricity. For any
extracts taken from the above, he tenders sincere thanks to the
authors, editors, and publishers of the same.
W. R. B.
NOTE TO SECOND EDITION.
For the present edition the book has been enlarged by the
addition of two new sections (III. and VII.), introducing additional
information in regard, more especially, to Central Station lay-out,
which cannot fail to increase the sphere of usefulness of the volume
amongst Central Station Engineers and their assistants.
The Author has to acknowledge here, with thanks to the Editor
of Electricity, the permission to utilise a certain portion of the matter
appearing in Section VII. which has already appeared in that
journal.
W. R. B.
CoRONADo, Sak Diego,
Califobku, U.S.A.
igoS.
)vGoo'^lc
CONTENTS.
INTRODUCTORY SECTION.
latroductory Terms and Explanations— Dynamo— Motor— Continuous or
Direct Current Generators — Alternators — Alternating Current Generators-
Cycle — Periods— Periodicity — Frequency — Multipolar Machines — Object of
— Frequencies Adopted in Practice — Standard Direct Current Pressures —
Standard Frequencies — Fundamental Formula in Dynamo Design — •' Single
Phase" Alternators— " Multiphase " or "Polyphase" Alternators — "Phase
Difference " — Quadrature — Two-phase — Di-phase— Three-phase — Tri-phase
— Mean Value ol E.M.F. and Current in Alternators — Maximum and
Minimiira Values — Average or MeanValue—"Vinnal" Volts and Amperes —
Effect of Self-induction and Capacity — Actual Power — Apparent Power —
"Power Factor" — Impeding or Retarding the Current — Condenser —
AccelerateorLead the Current— -Lag and Lead — Self- Inductance— Impedance
— Choking Coil — Transformers— Step-up — Step-down — Mutual Induction —
Laminated Magnetic Iron Circuit — Primary and Secondary Circuits — Ratio
of Transformation— Motor — Generator— Ratio of Windings— Cross-sectional
Area of Conductors — Rotary Converters — Booster — Battery-charging Booster
— Feeder Booster — Balancer Booster — Reversible Booster — Balancers —
Equalisers — Synchronous Motors — Synchronism — Asynchronous Motors —
Asynchronism — Advantages and Disadvantages of Gach^Induction Motors
— Slip — Alternators in Parallel — Synchroniser - . - - pp. i — n
SECTION I.
Continuous Current Dynamos — Series, Shunt, and Compoond- Clockwise
and Counter-clockwise RotatioQ of Armature — Starting and Stopping —
Series Wound Dynamo — Shunt Wound Dynamo — Compound Wound
Dynamo — Diagram of Connections of a Series, Shunt, Short Shunt, and
Long Shunt Compound Machines — Shunt Wound Dynamo on a Constant
Po ential Circuit Supplying Incandescent Lamps in Parallel — Series Wound
Dynamo on a Constant Current (Variable Potential) Circuit with Lamps in
Series (Arc Lamps) — Two "Shunt Wound" Dynamos in Parallel on a
Constant Potential Incandescent Lighting Circuit — T-wo Compound Wound
Dynamos Connected in Parallel on a Constant Potential Circuit— Methods
of Securing Right Polarity of Dynamos — Lamp Method— Voltmeter Method
—Testing Polarity (Positive) of a Dynamo— Effects of Changing the Direc-
tion of Rotation of the Armature — Clockwise and Counter-Clock wise Direction
in Shunt, Series, and Compound Dynamot .... pp, n — 25
,„„: b, Gooi^lc
SECTION II.
Direct Current Motors — Constaat Potential Molors on Coostani PotentUI
Circuits— Series and Shaiit— Speed RegaUtioii of Shunt Motor— Short
Circuiting Device for M^net Coils — Shunt Regulator— Clockwise and
Counter-Clockwise Direction of Rotation at the Armature in Series. Shunt.
and Compound Motors — Differendal Wound Compound Motor to Produce
Constant Speed - - pp, a6 — 35
SECTION III.
Two- and Four-Polo Shunt Motor and Auto-Starter — Motor with Shunt,
Field Regulator, and Starting Switch— Four-Pole Shunt Motor with Com-
routating or Compensating Fol«s — Fonr-Pole Compound Molor with Auto-
Starter— Reversible Series MotOT'-Reversible Shunt Molar — Compound
Motor and Controller — Compound Dynamo with Compensating or Com-
mutatiiig Poles— Sii-Pole Ccmpound Djnamo Circuit, &c. - pp-36— 43
SECTION IV.
Electric Traction— Controllers— Motors— Tramway Circalt— !Jeries-Parallel
Controller— Electric Brake — Accumulator Cars — Electric Vehicles — Series-
Motor — Diagram of Electric Tramway Circuit — Series Motors in Series and
Parallel — Controller Method of Commuting the Field Magnet Coils — Develop-
ment of the Controller, showing Various Combinations — '• Series-Parallel "
Controller — Connections and Diagram of '■ S.-P." Controller — Combinations
Efifected by " S.-P." Controller— Electric Brake— Right and Wrong Methods
of Connecting— Controller Connections to Produce Braking Effect— Brush
System of "Series-Parallel" Controller and Wiring — Car Wiring Diagrams
andControllerConoections— Electric Vehicle "S.-P." Controller Connections
— Development of the Controller — Accumalalor Cars and Electric Vehicles
with Storage Batteries (Accam'ilators) — Biaka Rheostat — Saries Motor and
Coatrolier-^Daveloptneat of Westinghoose Controller and Motor Circuits,
Ac. pp. 4*— 69
SECTION V.
Combined Lighting and Power Schemes, with Batteries. Boosters,
Balances, &c., Direct Current — End Cell Switches — Object o(— Charge and
Discharge End Cell Switches — Dynamo. Booster, and Battery Connections —
Regulation of Pressure on the Three-wire System by Means of Balancers
(Equalisers)- Balancers and Storage Battery — Three-wire Direct Current
System with Storage Batteries and Boosters— Lighting Plant with Storage
Batteries — Booster and Storage Battery Plant — Three-wire, Booster. Biltery.
and Feeder Connections — Reversible Booster Arranged for Lighting and
Traction Work — Highfield Booster Laminated Field Magnets of Reversible
Booster, ic. pp. 70—86
SECTION VI.
Alternating; and Polyphase Currents— Power Transmission— Synchronising
—Paralleling of Alternators — Mntual Induction— Primary and Secondary
)vGoo'^lc
CONTENTS. vii
Circuits— Synchroniser— Synchronising Alteroators— Frequency, Unison, in
Step, Phase— Methods of Collecting Currents from Two-phase Generators —
Polyphase Currents — "Triangular" or "Mesh" and "Star" Connections
of "Three-phase" Circuits — First, Second, and Third Phases— Polyphase
Transmission of Power — Star and Mesh Methods— Two-phase Transmission
with Poor Wires and Three Wires— Three-phase Transmission with Sin,
Four.and Three Wires— "Phase-difference" Methods of Starting " Single-
Phase" Motors by Means of Auxiliary Phases, with "Self-induction"
and " Capacity " in the Circuits — Choking-coils and Condensers — Reversal
of Direclioo of " Single-phase " Motors — Operating " Three-phase" Motor;
on "Single-phase" Current Supply — Rot«ry Converters and Transformer
Polyphase Connections — "Two-phase," "Three-phase," and " Six-phase "
Methods — "Three-phase" Distribution for Power and Ljghling — "Star
Methods" Low-tension Distribution — "Three-phase" and " Single-phase"
Three-wire Systems— Working of Alternators in Parallel — Method of Starting
Synchronous Motors or Rotary Converters — Paralleling "Two-phase" and
"Three-phase" Generators— Canal Haulage by Means of Electricity —
"Single-phase" Pumping Plant — Rotary Converters on "Three phase"
Circuits — Polyphase Machinery Connections— Alternating Current Switch-
board Connections — Alternating Current "Sub-station" Connections-
Application of Polyphase Currents to Electric Traction — Paralleling of
Alternators- Two-phase and Three-phase Motors and Starters— Starting and
Stopping— Development of Controller and Motor Circuits, &c. pp. 87—126
SECTION VII.
Fault T«At Panel — Traction Switchboard — Board of Trade Test Panel-
Testing Tramway Circuits — Three-phase Switchboard — Three-phase
Synchronising Gear — Synchronising — Single-phase Alternator and Exciter —
Single-phase Alternating Current Switchboard — Combined Lighting and
Traction Switchboard ^- Booster and Battery Circuits — Paralleling of
Balancers — Operation and Manipulation of Balancers and Boosters —
Battery Charging, Sc. -.-.---. pp.127 — '^
„Gooi^lc
„Gooi^lc
LIST OF ILLUSTRATIONS.
1. Series Wound Dynamo
1. Shunt Wound
]. Compouad
4. Series Dynamo Connections
3. Shunt
6. Compound Dynamo, Series and Short ShnnI Connections .
7. Compound Dynamo, Seriea and Long Shunt Connections .
8. Shunt Wouad Dynamo on a Constant Potential Circuit . ,
9. Series Wound Dynamo on a Constant Current Circuit
to. Sbuat Dynamos in Parallel on a Constant Potential Circuit
II. Compound Dynamos in Parallel on a Constant Potential Circuit
(2. Testing Polarity of Dynamos, l-ainp Method
13. Testing Polarity ol Dynamos, Voltmeter Method ....
14. To find Positive Pole of a Direct Current Dynamo ....
15. Clockwise Rotation of the Armature in a Shunt Wound Dynamo
16. Counter Clockwise Rotation of the Armature in a Shunt Wound
Dynamo
17. Clockwise Rotation of the Armature in a Series Dynamo
i8. Counter Clockwise Rotation of the Armature in a Series D3mamo
ig. Clockwise Rotation of the Armature in a Compound Dynamo .
20. Counter Clockwise Rotation of the Armature in a Compound Dynamo
31. Shunt Wound Motor on a Constant Potential Circuit .
32. Series Motor on a Constant Potential Circuit
23, Speed Regulation of Shunt Motor
2+. Short Circuiting Device for the Magnet Coils
35. Counter Clockwise Rotation of the Armature in a Series Motor .
36. Clockwise Rotation of the Armature in a Series Motor
37. Clockwise Rotation of the Armature in a Series Motor
28. Counter. Clockwise Rotation of the Armature in a Shunt Motor ■
2g. Clockwise Rotation of the Armature in a Shunt Motor
30. Clockwise Roiaiion of the Armature in a Shunt Motor
JOA. Two-pole Shunt Motor with Auto-Starter
30B. Four-pole Shunt Motor with Auto-Starter
30c. Four.pole Shunt Motor with Shunt Regulator and Starling Switch
30D. Jour-pole Shunt Motor with Commutating Poles
3oe. Fonr<pole Compound Motor with Auto-Starter
3oy. Reversible Series Motor
30G. Reversible Shunt Motor
30H. Compound Motor and Controller
301. Four-pole Compound Dynamo with Compensating Poles
30K. Six-pole Compound Dynamo
)vGoo'^lc
LIST OF ILLUSTRATIONS.
31. Electric Tramway Circuit ^3
32. Series Motors on Elec'ric Tramway Circuit .5
33. Series Motors Id Parailel on Tramway Circuit .7
34. Series Motors in Series on Tramway Circuit . . . . - 47
33, Controller Method of Commuting the Field Magnet Coils , . ■ 48
36. Development of Controller, showing the various Combinatioiis of the
Circuits ^g
37. " Seriea-Parallel" Controller ci
38. Connections of " Series- Parallel " Controller ^j
39. Diagram of " Series- Parallel " Controller j3
40. Combinations effected by the " Series- Parallel " Controller. . . ^4
41. Series Motor Connections j6
42. Electric Brake, Wrong Method of Connections 57
43. Electric Brake, Right Method of Connections .... 37
44. Connections to Produce Barking Effect jS
45. Brush System of ■■ Series-Parallel " Controller 59
46. Brush System of Controller Wiring 59
47. 4S. Braib System of Car Wiring 60
49. Brush Standard H, System of Controller Connections. . ■ • 61
50. Brush Hj Diagram of Controller Wiring , ■ • • • ■ 62
51. Rrush Hg System of Complete Wirii^ Connections .... 63
51. Wiring Diagram of the British Engineering Company's Controller . f,^
53. Wiring Diagram of Kj Controller g.
54. Wiring Diagram and Controller Coonectiors, Dick-Kerr System . gj
55. Electric Vehicle, " Series-Parallel " Controller Connections . . 66
56. Development of the Controller . 67
36*. Development of Westinghouse Controller .... jacmgp. 68
j6b. Four-pole Series Motor with Controller C3
57. End Cell Switch 7°
38. Combined Storage Battery Plant 7'
39. Dynamo, Booster and Battery Connections .... -7^
60. Balancer on Three- Wire System 73
61. Three- Wire System with Balancer 74
6a. Three. Wire Distribution with Balancer and Storage Battery . . 75
63. Three-Wire Direct CurrenI System with Storage Batteries and
Boosters 77
64. Lighting Plant with Storage Batteries 78
65. Booster and Storage Battery Plant 79
66. Three- Wire. Booster, Battery and Feeder Connections . . -Si,
67. Reversible Booster arranged for Lighting Work 82
68. Reversible Booster as arranged for Traction Work .... 84
69. Reversible Booster as arranged for Traction Work .... 85
70. Synchroniser 87
71. "Synchronising" Alternators 88
7a. Method of Collecting a Current from a Two-phase Generator . . gg
73. Another MethodofCoUecting a Current from aTwo-phase Generator, gg
74. "Triangular" or"Mesh" ConnectionofaThree-pbaseCircuit , ^
7j, " Star " Connection of a Three-phase Circuit go
76. " Star" Method of Polyphase Transmission of Power . . . ■ gi
77. ■•Mesh"Methodof Polyphase Transmission of Power . • • gi
)vGoo'^lc
UST OF ILLUSTRATIONS.
78. Two-phase Transmission with Four Wires 93
79. Two-phase Transmission with Three Wires ■ ■ ■ • ■ 93
Bo. Three phase Transmission with Six Wires 94
81. Three-phase Transmission ■' Star " Connected with Four Wires 93
8a. Three-phase Transmission "Star" Connected with Three Wires . 95
83. "Phase-difference" Method of Starting Single-phase Motors by
means of Self-induction inserted in Circuit g6
P4, '• I'hase-difference " Method of Starting Single-phase Motors by
means of Capacity inserted in the Circuit 97
S5. Method of Connections, so as to caase a Reversal of the Direction of
Rotation of a Single-phase Motor . ' 98
86. Another Method of Connections, so as to Cause a Reversal ol tlie
Direction of Rotation of a Single-phase Motor . . . . ^
87. Method of Operating a Three-phase ftlotor on a Single-phase
Current Supply 09
88. Rotary Convener and Transformer, Polyphase Connections. Two-
phase Method 100
89. Rotary Converter and Traaaformer, Polyphase Connections. Three-
phase Method toi
90. Rotary Converter and Transformer, Polyphase Connections. Three-
phase, a Second Method loi
gi. Ditto as above, a Third Method loz
93. Rotary Converter and Transformer, Polyphase Connections. Six-
phase Method 102
93. Rotary Converter and Transformer, Polypbase Connections. Six-
phase, a Second Method 103
94. Ditto as above, a Third Method 103
93. Ditto as above, a Fourth Method j^.
96. "Star" Method of Three-phase Distribution for Power and Lighting. 105
97. Low-tension Three-phase System for Power and Lighting , . . 106
98. Low-tension Distribution by the Single-phase Three-Wire System . 106
99. Single-phase Alternators in Parallel loj
100. Method of Starting Synchronous Motors or Rotary Converters . 108
loi. Paralleling Two Two- phase Generators log
103. Paralleling Two Three-phase Generators no
103. Transformer and Rotary Converters for Canal Haulage . . .111
104. Single-phase Pumping Plant [13
105. Rotary Converter on Tliree-phase Circuit ...... ,j^
106. Polyphase Machinery Connections li>
107. Alternating Current Switchboard Connections 117
108. Alternating CtlrreUt Sub-Station Connections . . . , . uS
109. Polyphase Currents applied to Electric Traction ..... 120
no. Paralleling of Altematocs 121
111. Paralleling of Alternators m
112. Two.phase Motor with Starter J22
113. Two-phase Motor with Starter 123
114. Three-phase Motor with Starter 124
115. Three-phase Motor with Controller 1^5
116. Development of Three-phase Motor and Controller . . .126
1J7. Development of Three-phase Motor and Controller , . facmg p. 126
)vGoo'^lc
LIST OF ILLUSTRATIONS.
Faalt Teat Panel . laS
Traciion Switchboard 129
Board of Trade Test Panel 131
Tesiing Tramway Circuits 134
Three-phasa Switchboard 137
Three-phase Synchronising Gear 139
Single-phase Alieraator with Exciter 14a
Singlo-phasa Alternating Current Switchboard . . . facing p. 141
Single-phase Alternating Current Switchboard 141
Combined Lighting and Traction Switchboard , , . facing p. 148
Booaier and Battery Circuit 153
Paralleling of Balancers 157
Booster and Battery Circuit 13S
)vGoo'^lc
^ OF TH€
UNIVERSITY
Of
DYNAMO, MOTOR AND SWITCH-
BOARD CIRCUITS FOR ELECTRICAL
ENGINEERS.
INTRODUCTION.
I. — A Dynamo is a machine which converts mechanical energy
into Electrical Energy.
A Motor is a machine which converts Electrical Energy into
Mechanical Energy.
3. — A dynamo and motor are mutually convertible; that is, a
dynamo will act as a motor if supplied with electrical energy, and a
motor will act as a dynamo it driven mechanically, or, in other words,
the same piece of apparatus will act both as a dynamo and as a
motor, which depends upon whether it is supplied with mechanical
or electrical energy.
Generally, a well-designed efHcient dynamo becomes a good motor
when so used.
3. — Dynamos may roughly be divided into two classes : first, those
in which they supply a current of electricity, which flows in one
continuous direction through the circuit external to the machine,
these are known as continuous or direct current generators or
dynamos ; and secondly, those which supply a current which
rapidly alternates or reverses its direction through the external circuit,
these are known as Alternating Current Generators, shortly
termed Alternators.
The variation of the E.M.F. during the rotation of the armature
conductor over one pair of poles is termed a " Cycle " ; the
)vGoO'^lc
S DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
number of " cycles " or " periods " passed through in one second
is termed the " periodicity " or " frequency" of the alternating
currents.
4. — Alternating current machines are generally constructed
with a multiple of pairs of poles, and are generally called " multi-
polar machines." Theobjectofthisis to increase the "frequency"
and E.M.F. of the machine without increasing the speed, because
there is a practical limit as regards the safe speed at which moving
masses of machinery may rotate or move ; the larger the machine,
the slower the speed.
As previously stated, the variation of E.M.F, during one revolu-
tion of the armature coil when passing over one pair of poles is called
one " cycle " ; by employing two pairs of poles, the number of
"cycles" or the "periodicity" or "frequency" is doubled; with
three pairs of poles it is trebled, with eight poles (four pairs)
quadrupled, &c.
5. — To find the " fi-equency " or " periodicity "of an alternator,
the number of revolutions per second must be multiplied by the
number of pairs of poles ; for example, if the speed of an eight -pole
alternator is 600 revolutions per minute, this divided by 60 := 10
revolutions per second ; it has four pairs of poles, therefore its
firequency is 4 X 10 = 40 cycles per second.
The frequenciesof practical machines vary between about 25 to 120
cycles per second.
Now, each " cycle " consists of two alternations or reversals ;
therefore the number of alternations is equal to twice the number
of cycles. In the above case, the number of alternations or reversals
per second = 2 x 40 = 80.
6.— The following ate somi
practice : —
Niagara
Westinghouse Company
Dublin Electric Tramway
Brown, Boveri & Co.
of the frequencies adopted in
25 cycles
25 to 60 „
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 3
Ganz & Co., of Buda-Pesth 42 cycles per second
The Allgemeine Electricilats-
Gesellschaft, Berlin 50 „ „ „
Oerlikon Maschinenfabrik 50 „ „ ,.
General Electric Company, America 60 „ „ „
Different companies in Great
Britain 35 to ipo „ „ ,,
It wUI be seen from the above list that there is a very wide range
in the number of " cycles " per second between the " minimum " and
" maximum " periodicity adopted by different manufacturers. This
is a great disadvantage, considered both from a commercial and
practical standpoint. With a view to standardising the electrical
pressures and frequencies of electrical machinery, there has recently
been appointed an Electrical Engineering Standards Committee, for
the purpose of discussing the pros and cons, of this important subject.
The following are their recommendations on standard direct current
pressures and standard frequencies : —
(i.) That the standard direct current pressures, measured at the
consumers' terminals, be no, 220, 440, and 500 volts.
(a.) That the standard direct current pressures, measured at the
terminals of the motors, be — for tramways, 500 volts; for rail-
ways, 600 volts.
(3.) That 25 periods per second be the standard '* frequency "
for—
(a.) Systems involving conversion to direct -currents by means ot
rotary converters.
(6.) Large power schemes over long distances.
(«.) Three-phase railway work, where motor gearing and the
' inductive drop on the track rail have to be considered.
(4.) That 50 periods per second be the standard " frequency "
for—
(a.) Mixed power and lighting on town supply mains.
(J.) Ordinary factory power plant.
(c.) All medium-sized power plant where rotary converters are not
employed.
The importance of this standardising of conditions both from
a manu^turing, commercial, and practical standpoint cannot be
overestimated.
)vGoO'^lc
4 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
7. — In dynamo machine design there is a. fundamental formula
connecting the number of lines of force of the magnetic circuit, the
number of revolutions per second, the number of conductors around
the armature, and a constant 10'= 100,000,000. From these we cau
get E, the E.M.F. in volts.
Let N. represent the total number of lines of force. C. = con-
ductors around armature, « = the number of revolutions per second.
Then
„ „ C. X n.
E.=N.x -^^
10* is a constant, and is the relation between the absolute or
fundamental unit and the practical units of E.M.F.
The above formula explains why it is that we can obtain a
greater E.M.F, by increasing the number of lines of force without
increasing the speed, and if we wish to obtain the same E.M.F.
and reduce the speed, we can do it by increasing the m^netic lines
of force round the magnetic circuit.
8. — There are simple "single phase " alternators, also "multi-
phase" or "polyphase " alternating currents.
If we have two alternating currents whose " phase " differ-
ence is one fourth of a period, or one current liigs behind the other
90 degrees, they are said to be in " quadrature," and this con-
stitutes what is technically termed a " two-phase " or " diphase"
current; if we have three alternating currents which differ one
third of a period in phase or have a relative phase difference
of 120 degrees, they are known as "three-phase" or "tri-
phase " currents. We may also have " three-phase " currents
which lag 60 degrees behind each other.
9. — Mean value of E.M.F. and current in (^Umators.~ln an
alternator the voltage or E.M.F. in the outside circuit does not
reach either the " maximum " or " minimum " amount which it
attains in the armature, but rather an average or a mean value,
which, under the most favourable conditions, is about -j^ of the
" maximum " value which the E.M.F. reaches in the armature.
The current strength is proportional to the E,M,F. ; therefore its
average current strength in the external circuit is about ^ of the
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 5
" maximum " current in the annature. These are called
" virtual" volts and amperes.
10. — To determine the power furnished by a continuous current
dynamo, we can obtain it by measuring the volts by means of a
voltmeter, the amperes by an ammeter; and multiplying the two
together gives us the power in watts. But in the case of alternating
current machines we have effects due to the influence of "self-
induction" and "capacity" of the circuit, which makes it that
the current flowing at any given time may be the result of an
E.M.F. which existed some interval of time before or after that
time.
II. — The actual, real or effective power or watts, measured
at any time, is the number of volts multiplied by the number of
amperes given off at that time, while the power obtained by
multiplying the average voltage by the average current is
always greater than the actual ponrer, and is termed the appa-
rent power or watts. Now dividing the " maximum " value of
the actual power by the apparent power, we obtain the " power
factor " of the alternating current circuit.
Power factor = true watts.
apparent watts.
The " Power factor " is that quantity which when multiplied
by the apparent watts gives the true watts.
The power factor will depend upon the nature of the circuit, and
the kind of machinery or resistances supplied by it. " Self-
induction " and " capacityS: affect the power factor of a
circuit. ^~y
The actual or true watts n»y be measured directly by means
of a suitable wattmeter. L
The true watts can also be obtained if we know the " ohmtc
resistance " of the circuit, and the amperes flowing as indicated
by an amperemeter (virtual amperes).
fur true watts ^ Current squared x Resistance
= Av^ X R.
Where Av^ virtual amperes squared x Resistance in ohms.
)vGoo'^lc
) DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS
ExampU, — Ammeter reading = 120
Voltmeter = 100
Apparent watts = 120 x 100 = 12,000.
Assuming the wattmeter to read 11,520 = real or true watts.
Then Power factor = "°"""'-
apparent watts.
Example. — To find the power factor, when the actual power as
indicated by a " wattmeter " is 8000 (true watts), and the average
E.M.F. measured by a voltmeter 100 volts, and the average current
measured by an ammeter is 100 amperes. The apparent power is
100 X 100 = 10,000 watts.
.*. power factor *± _>°o° _ .g qj gg -g, cent.
10,000
Now if the current lags behind the E.M.F. we can readily find
the actual or true watts (without using a wattmeter) if we know
the angle of lag, and the virtual volts and amperes, as indicated
by a voltmeter and amperemeter.
for true watts = F„ x C, x cos. X
= Volts ,irt^ X amperes rttuai X cos. X,
where cos. X = the cosine of the angle of lag,
where X = angle of lag.
Example, — Suppose the voltmeter reads 100 volts, and the am-
meter 10 amperes, while the current is known to lag 60° (" angle
of lag = 60" " = " cos. \" =" COS. of angle 60° ") (where numerical
value of COS. 60" = X) ; referring to a table of cosines it will be
found that the numerical value of the cosine of this angle (60°) =-5
.'. true watts = 100 x 10 x -5
= 500
and apparent watts = 100 x 10
= rooo
power factor = ^522. = -5 := value of cos. 60° := angle of lagX.
DiqmzecbvGoO'^lc
DIRECT, ALTERNATING, AND POLYPHASE. 7
Therefore cos. \ may be considered to be the " power &ctor " of
the circuit.
or power factor = «""^""
apparent watts,
or cos i ^truewatte
apparent watts.
, • . numerical value of cos. \ = power factor.
For instance, suppose the value of the angle cos. A = -9 and we
have the amperemeter and voltmeter reading 10 and 100 respectively,
the true watts = C, x F, x cos. A,
= 10 X 100 X '9 = 900,
and apparent watts = 10 x 100 = 1000
but we already have cos. A = -g,
. • . COS. X = power factor.
13. — There are two properties of a circuit which have certain
actions in relation to alternating currents. These are the effects
of "self-induction" and "capacity." The effect of "self-
inductance " in a circuit is to decrease and impede or retard
the current. Every circuit possesses more or less "capacity,"
and is a condenser ; the effect of " capacity " is to increase and
accelerate or lead the current before the E.M.F. Therefore
an alternating current flowing in a circuit possesstbg considerable
"8elf-inductance" will lag or fall behind the impressed E.M.F.
causing it, and when traversing a circuit having considerable
" capacity " will be in the " lead " or travel in front of the
impressed E. M. F. causing it We can, therefore, by inserting into
a circuit possessing self- inductance a condenser of suitable
capacity, cause the impedance to be diminished and the current
strength increased, and also by inserting a piece of apparatus
possessing self-inductance, such as a choking or impedance
coil, cause the impedance to be increased and the current
strength diminished. We see that inductance and capacity
produce opposite effects, and can be used to neutralise each
other's effects. By suitably choosing a capacity and inductance
of equal amount, the current neither lags nor leads, and the
current is s£ud to be in phase with the E.M.F. The angle of lag
)vGoO'^lc
8 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
is the technical term used to denote the angle " 6 " by which the
current laga behind the E.M.F., »>., 6 is the " angle of lag."
The " angle of lead " is the term used to denote the angle " 6 "
by which the current leads the E.M.F., w., 6 is the " angle of
lead."
13. — In addition to the above-mentioned apparatus, there are
transformers which transform alternating currents from one
I voltage to another. If the alternating current is increased in voltage,
it is called a step-up transformer; and if the voltage is lowered
or decreased, it is called a step-down transformer. The principle
1 of transformation depends upon mutual induction, and a trans-
I former consists simply of a laminated magnetic iron circuit
to form a good permeable path for the magnetic lines of force over
I which two separate coils of wire are wound ; these are called the
primary and secondary circuits or windings. In the case of the
step-up transformer the primary consists of a comparatively
few turns of thick well -insulated copper wire, and the secondary
circuit of a great many turns of fine well-insulated copper wire ;
in the step-down transformer it is vice vers&. That circuit
is called the primary circuit to which the terminals of the inducing
current are connected, and the secondary circuit is the circuit in
which the current is induced by the mutual induction due to the
primary current.
14. — The ratio of transformation is the ratio of the trans-
formed to the original voltage, and theoretically depends upon the
ratio of the number of turns of the primary and secondary windings.
If we wish to transform down from 2,000 volts in the primary to
100 in the secondary, the ratio of transformation is 20 to i, and the
comparative number of turns on the primary and secondary would
be as 20 to i.
The current increases and decreases in the same ratio aa the
voltages decrease and increase (neglecting stray losses).
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 9
For transforming continuous currents from one voltage to another,
a machine called a motor- generator is' used. It is a combination
of a motor and a dynamo, generally combined together in the
form of one single machine which has two separate windings on
the armature, with a commutator and pairs of brushes at each end.
The number of conductors in the primary and secondary wind-
ings are proportional to the ratio of the incoming and outgoing
voltage, and the cross-sectional area of the armature conductors
are in the inverse ratio, because the current strength is transformed
inversely as the voltage.
15. — ^To transform alternating currents to direct or con-
tinuous currents, and vice versa, we use what are called rotary
converters, which is 3 piece of apparatus equivalent to a combined
direct current dynamo and an alternator, one winding in combination
with the magnetic field, acting as a motor to drive it, the other
winding (armature) acting as a dynamo or generator.
16. — A " Booster " is a dynamo driven mechanically (usually
by means of a separate motor) to the terminals of which is con-
nected a source of supply of a current at a certain volt^e, and by
means of the "Booster" its voltage is raised from its original
voltage to any desired voltt^e. For example, it can be used to
raise the voltage of a source of supply from 100 volts to 150 volts,
&c. Boosters are generally used in combination with storage
batteries on electric light and traction circuits.
There are "Battery-charging Boosters," " Feeder
Boosters," " Balancer Boosters," &c.
A " reversible " Booster either adds to or subtracts from the
line voltage.
"Balancers" or "Equalisers" are motor dynamos with
equal windings. They are used to keep balance between the two
sides of a three-wire system.
17. — There are single-phase alternating current motors,
called synchronous motors, because they work in synchronism
with the generator. They have two great disadvantages : (i) they
are not self- starting, and must be brought up to the proper speed
)vGoo'^lc
lo DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
before being connected in circuit; and (2) their field magnets must
be separately excited.
Two-phase fdiphase) Motors and Three-phase (triphase),
Motors (polyphase current motors), the principle of action of which
depends upon a rotating or rotatory magnetic field, are self- starting,
and are called " asynchronous motors." There are two chief
parts composing the apparatus, one part at rest, called the " stator,"
the other part rotating, called the " rotor."
18 — Synchronous and Asynchronous. — Both single-phase
and polyphase motors may be divided into two distinct classes,
ia., "synchronous" and "asynchronous" motors. The
synchronous motor is one which runs perfectly " in step," or
" phase," or synchronism with the alternating current supplied and
consequently runs at a constant speed. The "asynchronous"
motor does not run in synchronism with the alternating current
supplied. Any alternating current generator can be run as a
synchronous motor. The single-phase synchronous motor is simply
a single-phase alternator reversed, which when., its armature is
supplied with an alternating current, and once run up to a constant
speed, so as to be in synchronism with the generator and has its
field -magnetism excited with a direct current, may be fully loaded
and do work without being thrown out of synchronism. For long-
distance transmission of power, and constant speed, and steady
running with variable torque, the single-phase motor is perfectly
adapted. There is a limit, however, to its use. (a.) It is not suitable
for cases where the power has to be divided into separate and small
units, (b.) It is not self-starting without special devices, as it has
practically no initial torque, (e.) There is a limit to the load which
It will take, and is liable to a sudden stoppage by a temporary over-
load, throwing it out of synchronism. The separate excitation by
continuous current is also a disadvantage. Many devices, however,
have been introduced to render this type of motor self- starting, and
in this way Its sphere of usefulness has been considerably enlarged.
Another disadvantage is that it requires an auxiliary power for
starting. On the other hand, it has certain advantages. Firstly, the
speed of the motor is very constant and uniform, a property very
desirable in certain cases, and secondly, the synchronous single-phase
motor has a great advantage over all other alternating current
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. n
apparatus, in the fact that no phase difference between voltage and
current is caused by it.
Owing to the above disadvantages, the two-phase and polyphase
motors have become formidable rivals. The distinguishing features
of the polyphase motors are — (i) the rotating magnetic field, and
(2) the initial torque due to the inductive action of the closed or
short-circuited armature coils or rotor. They are induction
motors. They require no commutator, and unless a special start-
ing resistance be used in connection with the "rotor" circuit, no slip
rings are required, as there is then no connection between the
external circuit and the rotor circuit. Without the starting resist*
ance these induction motors have sufficient starting torque to
enable them to start under load, and for general purposes they have
a fairly high efficiency. Motors of this class are known as " asyn-
chronous motors," and they are so called because their work-
ing principle depends on the fact that they do not run synchronously ;
but their speed is less than the speed of synchronism.
The difference in amount between the armature speed of an
"asynchronous" piotor and the speed of rotation of the field is
called the "slip." The " asynchronous " motor is self-starling
under load. The " slip " increases as the load increases. If the
"slip" at half-load (half normal load) is ij per cent., it will be
about 3 per cent, at full load. In practice a " slip " of from 2 to
5 per cent, is allowed.
We can get a variation of speed and variable starting torque
by inserting adjustable resictances in the "rotor" circuit by
means of slip rings.
19 When two " single-phase " alternating current generators
have to be run together in parallel to supply the same circuit as in
lighting circuits they must be in step or in synchronism before
they can be connected in parallel. It follows that the two alter-
nators must be run at the same speed, generate an equal voltage,
and be exactly in phase with one another. To indicate when one
machine is in synchronism with the other machine a piece of
apparatus known as a " synchroniser" is used.
)vGoO'^lc
SECTION I
CONTINUOUS CURRENT DYNAMOS.
MES, SHUNT AND COMPOUND — CLOCKWISE AND COUKTEK CLOCK-
WISE ROTATION OF ARMATURE — STARTING — STOPPING, ETC.
I. — In dealing with continuous current dynamos or generators, we
will only deal with those which are self-excited, with either the whole
or part of the current generated in the armature conductors.
2. — Series Wound Dynamo.
Fig. I represents the above. The external circuit and field coil
windings and armature are all in series with one another, and the
Main Circuit '
Fig. I. — Series Wound Dynamo.
whole of the current which goes through the external circuit also
goes through the field magnet coils. The field coils consist of a
few turns of thick wire of comparatively low resistance. If the
)vGoO'^lc
DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS. i3
external circuit is broken the field magnets receive no current, and
the machine fails to generate any current.
3. — Shunt Wound Dynamo.
Fig. 2 represents the above. The field magnet's windings or
coils are composed of a great many turns of fine wire, and form a
shunt to the external circuit ; their circuit is independent of the
external circuit, i.e., the breaking or opening of the external or
Shunl
p3
-Z^;^
'
l=(0)-
;
\ Shunl
I
Fig. a.—Shiiot Wound
Dynamo.
Fig. 3. — Componnd Wound
Dynamo.
m£un circuit does not open the shunt windmg or field circuit. The
field magnets take off only a small proportion 01 the whole current
4. — Compound Wound Dynamo.
Fig. 3 represents the above, which is a combination of the series
and shunt windings, or is excited partly by the series coils and
partly by the shunt coils. The object of compounding a machine is
to obtain a constant volt^e for incandescent lighting under variation
)vGoO'^lc
14 DYNAMO. MOTOR AND SWITCHBOARD CIRCUITS.
of load, Overcom pounding consists in winding with additional
series coils, the object being to maintain a constant voltage at a
[joint in the circuit which is some distance away from the generating
station.
Series
mmmmm
Shunt
External Circuit
Shunt
nAAAAAAAA/ wnaaaa/
External Circuit
■ -Long Stiuat
Compound
External Circuit
VVvAAAA/
Fig. 6.— Compound Dyna
^-m^ Series
Compound
External Circuit
VxAAAAA/
Fio, 7.— Compound Dynamo.
Series and Short Shunt Connections, Series and Long Shunt Connections,
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. ^5
5. — Series, Shunt, Short Shunt, and Long Shunt Compound
Machines.
Figs, 4, 5, 6, and 7 illustrate diagram matically a series, a shunt,
a short shunt compound, and a long shunt compound machine
respectively.
6. — Shunt Wound Dynamo on a Constant Potential Circuit
supplying Incandescent Lamps in Parallel.
Fig, 8 illustrates the above.
F.R, represents the field regulating resistance coils. A, is the
ammeter placed directly in series with the main circuit. V. is the
Shunt Woand Djnanio on a Constant Potential Circuit.
voltmeter, V.S. is the voltmeter switch ; there is also a main circiut
switch. To start the machine the main switch is open, it is then
run up to its proper speed and voltage, and the main switch is
then closed. The machine then supplies current to the main circuit.
To keep the voltage constant the resistance in F.R. is varied. Tc
stop the machine, if there is no chance of receiving current from
any other dynamo or battery, it should be slowed down and stoppeti
without opening the switches or lifting the brushes, after which the
switches may be opened. Never open the main circuit or switch oft
at full or partial load except ip case of emergency.
)vGoO'^lc
16 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
7. — Series Wound Dynamo on a Constant Current (Variable
Potential) Circuit with Lamps in Series (Arc Lamps).
Fig, 9 illustrates the above. The armature, main circuit, and
ammeter are all in series. To start it the main circuit switch must
be closed, otherwise it fails to generate ; to stop, same directions as
in par, 6.
8.— Two Shunt Machines Connected in Parallel on a
Constant Potential Incandescent Lighting Circuit.
Fig. 10 illustrates the above. The conditions are that the
voltages of the two machines must be equal, but the current in
->^
J
amperes given off by each machine may vary ; for instance, a 50-
ampere machine may be comiected in parallel with a 200-ampere
machine, providing the voltages are equal It is very important
that a dynamo before being connected into circuit when other
apparatus is already feeding it should be brought up to its proper
speed and voltage, otherwise it may short-circuit the system and is
very likely to burn o t its armature; its voltage should be about
I per cent greater or higher than that of the circuit. To start
the supply of current to the circuit, all the switches arc opened, the
nir.chine No. 1 is run up to its proper sp^ed and voltage and then
its main switch is closed This feuls the circuit by machine Na i.
To introduce machine No. 2, tun it up to its proper speed and
)vGoO'^lc
i>lRECT, ALTERNATING AND POLYPHASE.
voltage (about i per cent, higher) ; then close main switch of No. 2
machine. To stop, open main switch of No. 2 (if only small demand
Goot^lc
iS r}YNAlHO, MOTOk AND SWITCHBOARD ClUCVITS
is on circuit), and then machine No. i can be slowed down, and its
switch opened, or both machines can be slowed down tc^ether at
equal speeds, and then the switches opened
Shant Switch
i. II.— Compound Dynamos in Parallel o
a Constant Potential Circuit,
g. — Two Compound Wound Dynamos Connected in Parallel
on a Constant Potential Incandescent Lighting Circuit.
Fig. ri illustrates the above. A compound machine is a com-
bination of a series and shunt field winding, and we require switches
both in the series main circuit and also in the shunt circuit 5, is
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE.
19
the series switch of dynamo No. i , and 5^ is the series or nuun switch
of machine No. 2 ; there is in addition an equalising wire and switch,
which short-circuits the same polarity brushes of the two machines ;
its object is to keep the voltages of the two armatures equal, also
the currents in two series windings are equaU To place machine
No. I in circuit, close shunt coil switch and switch S^; then run up
the speed and voltage, when at the proper speed the proper voltage
will be attained. To introduce machine No. 2, close shunt switch
of No. 2; run up to proper speed and voltage; then close the
■Testing Polarity of Dynamos. Lamp Method.
" equalising switch," and then main series switch Sj. To stop the
machines, leverse operations.
10. — Methods of Securing Right Polarity of Dynamos.
When a dynamo has to be inserted in a circuit, and run in
parallel with either a secondary battery or another dynamo, it is
important to be certain that the leads are of the right polarity. If by
accident the positive of one machine was connected to the negative
of the other they would not be connected in parallel, but in series.
To test the polarity proceed as follows: run both machines up to
the same voltage; then close the switch j4 , of machine No. i {Fig. 12);.
)vGoo<^lc
20 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
then connect the terminals of two series connected normal voltage
lamps with the terminals of switch B. of machine No. 2 (switch B.
must be left open). If the polarity of both machines is all right, then
the lamps will not glow ; but if connected in series, the lamps will
brightly glow with their proper voltage. This indicates that the
Fig. 13. — Testing Polarity of Dynamos. Voltmeter Method.
machines are wrongly connected. The machines must then be
stopped, and the leads of one machine reversed.
Another method of finding the right polarity is indicated in Fig. 1 3.
Connect a "voltmeter" as indicated. Have both machines running
up to proper speed and voltage. Now close the " voltmeter " switch,
so that it indicates the voltage of first machine i, then machine 2.
If the pointer of the " voltmeter " is deflected in the same direction
in each case, then the machines are of the same polarity ; if it is
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 3'
deflected in opposite directions, then the machines are connected
up of opposite polarity- If wrongly connected, proceed as in the
previous case.
II, — Polarity of a Machine.
It is important sometimes to know which is the positive pole of a|
dynamo. This can be found by means of pole- finding paper. It is
made of paper which has been soaked in a chemical substance.
When the paper is wetted and included in a circuit the end of the
paper which is connected to the positive pole becomes discoloured a
certain colour. This is due to "electrolytic" action* Avery^mple
Fig, 14, — To find Positive Pole of a Direct Current Dynamo.
means of ascertaining which is the positive pole of a continuous
current dynamo is to take two clean strips of metallic lead, place
them side by side in a non-metallic vessel, fill up the vessel with a
dilute solution of sulphuric acid and water (about i part Hj SO^ to 10
of water), and connect this in circuit through a lamp with the
terminals of the dynamo. The lead plate connected to the positive
pole of the machine will, after a few minutes, become of a dark
chocolate brown colour, due to the formation of peroxide of
lead. The connections are indicated in Fig. 14.
)vGoo'^lc
23 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
la.— Effects of Changing the Direction of Rotation of the
Armature.
We must connect the magnet coils with the armature brushes in
such a manner that the current from the armature flows through the
+
^on
Fis. ij.— Clockwise notation of the Arroatnre In a Sbnnt Dynamo.
field mc^ets in such a directioD as to strengthen the field
magnetism.
13. — Shunt Dynamo : Clockwise Rotation of Armature.
Fig, 15 illustrates a shunt machine in which A. and B. represent
the brush terminals, C. and D. the field magnet terminals, and also
the shunt- regulating resistance.
In the figure h will be seen that the C. connection is connected to
A. terminal, and that the positive current flows downwards from C to
D. in such a direction as to strengthen the field magnetism. The
arrowheads indicate the direction of flow of the current both in the
external circuit and the field magnet circuit.
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 33
14 Shunt Dynamo: Counter-clockwise Rotation.
On referring to Fig. 16, it will be seen that if the direction of
rotation is now reversed, that the A. brush now becomes negative
(owing to the reversal of the current), whereas in the previous case
it was positive. The result is that if left connected to C, as in the
previous case, the current would flow through the field magnet coils
from D. to C, or in the opposite direction to what it flowed in the
previous case. The effect of this would be to destroy its original
Fig. 16. — Coanter-clockwlse Rotation of the Armatnre in a Shunt Dynamo.
magnetism. For this reason we have to connect terminal C. to
terminal B. (as shown in Fig. 16), and it will be seen, although the
current now flows through the external circuit in the opposite direc-
tion to what it did before, that it flows through the held magnets in
the same direction. This is exactly the condition required.
15 Series Dynamo : Clockwise and Counter-clockwise
Rotation of Armature.
On referring to Figs. 17 and 18, it will be noticed that the field
connection at C. has to be reversed from positive terminal of brush A.
)vGoo'^lc
24 DYSAMO, MOTOR AND SWITCHBOARD CIRCUITS.
Fig. 17.— Clockwise Rotation of the Armature in a Series Djmamo.
+
Fig. 18.— Coualer-tJockwise Rotation of tbe Armatare in a Series Dynamo.
DiqmzecbvGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 25
(in Fig. 17) to positive terminal of brush B. when the direction of
rotation is reversed (Fig. 18).
Fig. ig.— Clockwise Rotation of
the Armature in a Compound
Dynuno.
Fic 20. — Counter-clockwise
Eotarion of the Armature
in a Dynamo.
16. — Compound Dynamo: Clockwise and Counter-clock-
wise Rotation of Armature.
In this arrangement, we must change over both the shunt (C.) and
series (E.) field magnet connection from ^. brush terminal (Fig. 19
to positive B. brush terminal {Fig. 20) when the direction of rotation
is reversed.
)vGoo'^lc
SECTION II.
DIRECT CURRENT MOTORS.
SERIES, SHUNT AND COMPOUND — <X0CKWI5E AND COUNTER-CLOCK-
WISE ROTATION OF ARMATURE — SPEED REGULATION.
I, — Constant Potential Motor (Shunt-wound) on a Con-
stant Potential Circuit.
Fig. 21 illustrates the above. This is the commonest form ol
stationary motor, and will run at constant speed on a constant
potential circuit The field magnet coils are wound with the right
Flo. 31. — Shnnl-wound
Motor on a Constant
Potential Circuit,
size of wire to take the proper magnetising current, and if the
potential is constant the field strength will be constant. In con-
1 necting the motor in circuit, the field coils must be placed in circuit
. first, so that there is a certain amount of field magnetism, whereby
■.the mutual reaction between the field magnets and the armature
jcurrent causes rotation of the armature, and thus keeps the current
IRowing through the armature of a safe amount If the field
magnets were not put in circuit first, the armature at rest on
receiving current would probably bum ont, because the armature is
)vGoO'^lc
DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS a?
of very low resistance, and would take practically all the current j
supplied; there would be practically none go round the field \
magnet coils, no mutual reaction, and no rotation of the armature.
Therefore there is no counter- E.M.F. to keep back the excessive
current. The. apparatus and method of starting is shown in the
sketch. There is a branch circuit taken off the mains or line
through a double pole switch'; the connections can be readily seen.
To start the motor the double pole switch is closed. On pushing over
Ctltslaia Pal/ntial Cifttlt
—Series Motor on
a Constant Potential
Circnit.
the contact lever so as to make metallic contact with the circular arc
sliding contact blocks A. and £., it will be seen that the field leads
are placed in circuit first. This causes a suitable current to flow
through the field magnets, and they become excited. On further
rotating the contact lever, it places in circuit the armature through
the resistance coils R., R^, R^, R^, &c, Euid as the speed of rotation
of the armature increases the resistances are gradually cut out until
when in contact with Xi, the starting resistance is completely short-
circuited. To stop, reverse the operations.
a.— Series Motor on a Constant Potential Circuit.
Fig. 32 illustrates the connections. This motor 01
)vGoo'^lc
28 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
potential circuit does not have a constant field strength, nor yet run
at a constant speed. If the load is taken off entirely it will " race "
and run at an excessive speed. The electric tramway motors are
series-wound. They are only suitable where variable speed is
required, such as for elevators, pumps, fans, and railway work. The
machine is connected to the main circuit as shown. To start it, the
x>a
Starting Re^lator
Shunt Resistance
Fio. 33.— Speed Regulation of Shunt Motor.
circuit is completed through a starting resistance and switch S. J
fij, R^ are the resistance coils. To stop, reverse the operations.
3. — Speed Regulation of Shunt Motor.
The speed of a motor depends on the voltage of supply anc the
strength of its magnetic field. The motor tends to rotate so fast as
to produce a back or counter- E.M.F. nearly equal to the terminal
voltage. Therefore, if we double the terminal voltage, the motor
will run with nearly double the speed. By decreasing the terminal
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. ag
e of the motor we, therefore, decrease the speed of the motor.
This reduction of speed may be brought about by inserting a resist-
ance in series with the motor. By inserting this resistance in the
field circuit, the voltage at the terminals of the motor is lowered,
thus giving the condition necessary to reduce the speed. Fig. 23
illustrates an arrangement for varying the resistance and speed in
which we have a starting regulator and a shunt resistance regulator.
4, — Short Circuiting Device for the Magnet Coils, with
Shunt Regulator,
When a shunt circuit is broken, a much longer spark results than
in the case of a lamp circuit of equal current strength and voltage.
Fia. 24. — Short Circuiting Device for the Magnet CoUs.
This is due to an effect called " self-induction." Thus when we
break a shunt circuit a spark occurs, which results in the burning
away of the contact slip rings and the brushes of the starter. To
avoid this, the shunt circuit should never be broken with a current
on. A sparkless breaking of the motor circuit can only be effected
if there is at the moment of switching out no, (or a very small,)
pressure difference between the starting lever and the last contact.
Sometimes it is impossible to avoid the interruption of the shunt
)vGoO'^lc
30 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
circuit. In Fig. 24 is shown an arrangement to overcome the
difficulty in the case of a dynamo. It consists in closing the shunt
circuit on itself whilst it is being switched out, so that the " self-
induction "current may flow in the circuit so formed. The switching
out of shunt regulators must not be done suddenly, like the switching
out of starters. It should be done gradually, in order that the v
of the machine may decrease.
5.— Direction of Rotation of a Motor Armature.
To alter the direction of rotation of a motor armature, we have
either to change the direction of the armature current, or to reverse
H>i
Fig. 25.— Counter-clockwise Rolation of th« Armature
in a Series Motor.
the polarity of the magnetic field (Field Magnets). If we reverse
the armature current and the polarity of the field magnets simul-
taneously, the direction of rotation will of course, remain the same
as before.
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 31
6. -Series Motor: Counter - clockwist; Rotation of
Armature.
In Fig. 25 is shown the connections for a series motor which
rotates in a counter-clockwise rotation. The positive direction
of current flows from the starting lever and through the field
magnet coils from D. to C and in the armature from brush B.
to brush A., to which is connected the negative pole of the
feeder.
7.— Series Motor : Clock wise Rotation of Armature.
To reverse the direction of rotation of the armature, we may
either allow the current to Sow in its original durection (from D. to
Fio. a5.— Clockwise Rotation of the Armature in a Series Motor.
C.) in the field magnet coils, and alter the direction of the armature
current by changing the two connections on the brushes A. and B,
thus connecting field magnet terminal C. to brush A. and brush B,
with the second feeder wire, as shown in Fig. 26, or we may leave
the direction of the flow of current in the armature in its original
direction, and reverse that of the field magnet current, as shown
)vGoo'^lc
32 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
in Fig. 27. If we changed the mains or feeders leading to the starter
and to the motor directly, there would be no reversal of the direction
of rotation of the motor armature, because by so doing both the
axmature and the field magnet current would be reversed.
Fig. 27. — Clockwise Rotation of the Armature in a. Series Motor.
8. — Shunt Motor : Counter-clockwise Rotation of Armature.
Fig. 28 shows the connections of a shunt motor in which the
direction of rotation of the motor armature is counter-clockwise
The direction of the field magnet current is from D. to C, and the
armature current from B. to A. The positive main or feeder is
connected to the starter lever.
g — Shunt Motor : Clockwise Rotation of Armature.
To reverse the direction of rotation of the motor armature, the
current may be allowed to flow in its original direction through the
field magnet coils (from D. to C), but in the reverse direction through
the armature (from A. to B.), as shown in Fig. ag, or the direction
of the flow of current through the field magnet coils may be reversed
)vGoo'^lc
DIRECT ALTERNATING AND POLYPHASE. 33
S,R.
Fig. 38. — CoDDter-clockwise Rolatlon ol the Armature in a Shunt Motor.
+
Pic. 39. — Clockwise Rotatian of the Annatnre in a Shont Motor.
)vGoo'^lc
34 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
(from C. to D.), and the armature current flow i
direction (from B. to A.), as shown in Fig. 30.
the original
10. — Compound Motor.
A compound (series and shunt) winding of the field magnet coils
(Fig. 20) may be used on motors for various purposes. If the
current flows in the same direction through both the series and
shunt windings, then the combined effects of the two windings will
I. 30. — Clockwise RoCatioa of tbe ArmatDre in a Shunt Motor.
be to strengthen each other, consequently also the field magnetism.
This strengthening is greater the larger the armature current — i.e.,
the heavier the load^because an increased armature current, of
course, increases the current through the " series winding." Thus
the motor gets at increasing load a Stronger magnetic field; and
will, therefore, if the voltage remain constant, run slower than before.
For a given current the starting power of the "compound'' motor is
greater than that of a " shunt " motor. With a decrea^ng load the
motor will nm ^ter. The motor cannot " run away," however (the
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 35
same as a series motor), when the load is taken off entirely, because
the " shunt " winding produces a magnetic field of sufficient strength
to prevent it.
II. — Differential Wound Compound Motor to Produce
Constant Speed.
The speed of a " shunt-wound " motor does not remain absolutely
constant at all loads. Generally it decreases a little at increased
load. We may obtain a constant speed in a "compound motor"
with " variable " load by means of a " differential " winding, which
consists in so connecting the "series" and "shunt" windings that
they act in " opposition." The result is that, as the load becomes
heavier, the Aeld of the motor is weakened, and the armature runs
foster. On the other band, the motor would run slower at an
increasing load if it were a " shunt " motor only ; this fall of speed
is compensated by the action of the "series" winding. Thus a
compound wound motor (differentially wound) is capable of giving
a " constant " speed at all loads. Strictly speaking, this statement
is not absolutely true, because we get a variation of speed which
cannot be compensated by the series coil. This is due to the
rising " temperature " of the motor. This " variation " of speed,
due to temperature causes, can, however, be compensated by
inserting a variable resistance regulator in the " shunt " circuit, as
shown in Fig- 2j.
)vGoo'^lc
SECTION III.
TWO- AND FOUR-POLE SHUNT MOTOR AND AUTO-
STARTER.
MOTOR WITH SHUNT FIELD REGULATOR, ETC. REVERSIBLE SERIES
AND SHUNT MOTORS — COMPOUND MOTOR AND CONTROLLERS
COMPENSATING OR COMMUTATING POLES, ETC.
Fig. 30A.— Two-pole Shunt Motor (Direct Cnrrent Circnil) with AQto-Starter.
Description. — To start. — See that auto-starter lever is in "off"
position, close main switch,
" on " position.
To stop Open D.P. switch.
back to "oflF" position.
! starter handle from "off" to
Auto-starter will automatically fly
)vGoO'^lc
DIRECT. ALTERNATING AND POLYPHASE.
Shunt Winding
Fig. 30B. — Fonr-pole Shunt-wound Motor (Direct Cnrrent Circuit) with
Anto-Startiiig Rheostat.
)vGoo'^lc
38 DYNAMO. MOTOR AND SWITCHBOARD CIRCUITS.
NoVoltRekase
Shunt ^ind/njs
Fig. 30c,— Diagram of Conaections of Foiw-pole Shimt Motor on Direct
Current Circuit with Shunt Regnl&tor and Starting Switch.
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE.
Fig. 30D.—Four'po1e CimtiDiious CairenC VendUted Tjpe Shuot Motor,
with Auxiliary Com [nutating Poles. Motor ia variable speed and
used for Fan work.
Description. — To start. — See that the motor starter handle is in the
rest or "off" position. Close D.P. switch in main supply circuit ;
then gradually move the motor starter lever from " off" to full
"on " position. To vary the speed of the motor, rotate the contact
arm of the field rheostat.
To stop. — Open the main circuit by means of the D.P. switch.
)vGoO'^lc
40 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
Fig. 30B. — Fonr-pole Continnoiis Current Compound Motor.
Description. — To start. — Close the D.P. m^ switch; then slowly
move the motor starter lever from the " off" to the " on " position.
To stop. — Break the main circuit by means of the D.P, switch.
The starter will automatically release and fly back to the "o£F"
portion. If, when the motor is running, an overload should occur,
the maximum cut out will release the starting switch and break the
circuit.
^i^Vff
Ug.
i
L^l
i^^m
/re/a
ire
■ ITc.
Fig, 30F. — Conneclions for Reversible Series Motor.
Goot^lc
DIRECT, ALTHRNATING AND POLYPHASE. 41
fSe/a
\rc
ire.
Via. 30G.— Connectkmt for Reveruble Shnnl Motor.
[p
n
I zSe SA^Q 1
-OStnt, Ma-
Co^.^,^fi J>p L
+
m
„Gooi^lc
DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 43
)vGoo'^lc
SECTION IV.
ELECTRIC TRACTION, CONTROLLERS, etc.
MOTORS — TRAMWAY CIRCUIT — SERIES - PARALLEL CONTROLLER —
ELECTRIC BRAKE — WIRING DIAGRAMS — ACCUMULATOR CARS
ELECTRIC VEHICLES — MOTOR AND CONTROLLER CIRCUITS —
DBVELOPMBNT OF WESTINGHOUSB CONTROLLER, ETC.
I.— The Series Motor.
For electric trams and motor cars series motors are employed with
great advantage. The starting of an electric car can be effected
mote quickly with a "series" than with any other motor. The
"series" motor exerts its greatest "power" or "torque" when most
needed (jx., at starting). On " gradients " the car is running slower
and does not require so much current as one equipped with a "shunt-"
womid motor, whereas on the "level" the series motor enables the
car to run with a far higher speed.
3. — Digram of Electric Tramway Circuit.
Fig, 31 illustrates the method of transmitting electric power from
thepower house to the "overhead trolley line." Then the current goes
through the controller and motor and the return " rail " circuit back
to the power house or generating station. (Talcen &om the author's
book " Practical Construction of Electric Tramways," Spon.)
3. — Electric Tramway or Railway Motors and Controllers.
Electric street cars are generally equipped with two series-wound
motors. The voltage of the circuit usually adopted is about 500 volts.
To obtain "variations" in the "speed" and "torque," the
motors are sometimes connected both in "series" across the
drcuit, and sometimes both in "parallel" across the circuit. The
speed of a series motor depends upon its field strength; that is, it
varies with its magnetising force or with the number of ampere turns
on its field magnets. A method of regulating the speed is by
changing the field coil connections; ia, the number of ampere turns
)vGoO'^lc
DIRECT, ALTERNATING ANP POLYPHASE. 45
1 H
«=
^
^"1^
1 p
s 1
<l
t /"
^ Jl
%E
' c
If
■
\ ^.
1
h \\
^^ \
I li.
„Gooi^lc
46 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
is varied either by cutting out portions of the windings, or by the
combination of the field coils in various ways. In the commuted
field method, the field coils of the motor are wound in different
sections, divisions, or coiis (usually three). By connecting the field
coils of the motors in dliferent combinations the speed of the motors
is thus controlled. This different combination of the field coil
windings is effected by means of a controller or switch which consists
of a barrel upon which are fixed brass strips of various shapes, and
against these strips press spring contacts to make good electrical
connections with the barrel strips. In the starting of an electric
car it requires much greater force than is needed to keep it moving
after it has once been set in motion. Therefore the motors at
starting must be supplied with a comparatively heavy current. The
Fjg, 32. — Series Motors on Electric Tramway Circuit.
turning power (torque) of a series motor depends only upon the
strength of the current flowing through the armature circuit, and is
independent of the voltage across its terminals. If the two motors
are connected in one circuit, as in Fig. 33, with a current of, say; 50
amperes flowing through the two motors in series, they will give the
same starting effect or torque as 100 amperes flowing through the
two motors in parallel ; therefore by connecting the two motors in
series the motors will start with an expenditure of only one-half the
energy (electrical) that would be required if they were connected in
parallel This is because in series the motors only have one-half the
line voltage for each machine and 50 amperes, whereas in parallel
each motor gets the full line voltage and 50 amperes. When in
series each gets one-half the line voltage, becatise the total voltage is
equally divided between the two machines, but the "speed " of a
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 47
motor depends directly upon the electrical potential, or E.M.F., at
its terminals ; therefore the motors, when connected in series, will
only run at one-half their normal speed, and, in order to run the
cars at full speed or velocity, it becomes necessary to connect the
motors in parallel, so that each motor gets the full difference of
fnObfUne
Fig. 33.— Series Motora la Parallel on Tramway Circuit.
potential, or E.M.F. For this reason a " switch " is constructed by
means of which the motors are first connected in " series," so as to
start the car at half-speed with half the expenditure of energy, and are
then connected in " parallel," in order to run the car at full speed
without additional expenditure of energy. (The counter-E.M.F. due
Fig. 34. — Series Motors in Series on Tramway Circuit.
to the rotation of the armatures keeps the current strength down.)
Such a "switch" iscalleda "series-parallel" switch. Figs, ^^ and
34 show in a simple manner the two motors connected in " parallel "
and " series" respectively. When the motors are connected as in
Ftg. 33, they run at about double the speed when connected as in
Fig. 34, The torque or starting power is the same in each case. A
)vGoO'^lc
48 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS
method of commuting the field magnet coils is shown in Fig. 35,
It will be seen that there are seven different positions for the
contact springs on the barrel contacts. The development of the
controller, showing the various combinations of the circuits in
the seven different positions, is shown in Fig. 36. A, represents
the armature and brushes, a., b., and c. the divided field magnet
Fio. 33- — Controller Method of commntiiig the Field Magnet Cdla.
coils, L. the line connection, and G. the eartn connection in both
the Figs. 35 and 36. Similar letters refer to similar parts in
both figures.
4. — "Series-parallel" Controller.
In modem electric street or railway cars the "series-parallel"
switch is combined with a "field-controlling switch" and "regu-
lating resistance." Two of these are generally placed on each
car, one at each end, so as to control the car from either end.
There is also a small "reversing" switch on the controller, so
as to entirely reverse the current through the motors in case of
emergency; to avoid accidents, collisions, &c., and to bring the
car quickly to a standstill As before stated, the "series" motor
exerts its maximum torque when at rest, for then the strength
of the field and the strength of the armature current have both a
maximum value. As the motor begins to move it develops a
counter- E.M.F., which cuts down the current in the armature and
)vGoO'^lc
DIRECT, ALTERNAttNC AfiD POLYPHASE. 49
Diq.izeobvGoOi^lc
So DYNAMO, MOTOR AND SWlTCHBOAkl} CtHCUlTS.
in the field winding also, and the torque falls off, but resistance
can be slowly cut out of its circuit, so that the maximum current,
and therefore maximum torque, continues until it has reached its
normal speed, when all the resistance should be cut out of the
circuit. In this way we can so arrange that the motor will
start from rest, under full load, with a very large torque, and
continue to exert this torque till it gains full speed, the accelera-
tion, therefore, being very rapid, which is a point of the utmost
importance in traction work, where Che stopping and restarting is
very frequent.
The resistance to be added at starting absorbs a large amount
of power when the restarting is very frequent, such as is found
in the case of tramcars. This has led to an arrangement of the
motors in what is known as the "series-parallel" control. The
connections to the motors are made inside the " series -parallel "
controller {Fig. 37). (Taken from Tyson Sewell's "Elements of
Electrical Engineering," Crosby Lockwood.)
As before stated, one of these controllers is placed at each end of
the car. Inside this controller box is a long spindle, carrying a
number of stout brass or gun-metal segments, which make contact
for a longer or shorter time (according to the length of each) with a
corresponding number of spring contacts. The spindle is provided
at its upper end with a substantial handle, and the various contacts
are made by turning the handle through about 150 degrees. In this
case two motors are provided, and a small resistance. The first con-
tact joins both motors and the resistance in series on to the trolley
wire, which is usually at 500 volts difference of potential to the rails.
This allows the maximum current to ilow, and both motors exert
their full torque, but the moment they start they both generate a
back E.M.F., which is added together, for the motors are in series,
and so the current begins to decrease. The second contact cuts
out half the resistance and keeps the current at its original value,
even though there is now a back E.M.F. in the circuit, and the
torque still continues at a maximum. The speed therefore increases,
and the third contact cuts out all the resistance, and we have the two
motors in series only (see Figs. ^2 and 34), with the maximum current
still on. The next contact changes the connections from series to
parallel, and also inserts the whole of the resistance once more.
This is necessary, because in changing from " series " to " parallel "
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE.
51
tbe resistance is only one-quarter what it was, and the back E.M.P.
is also reduced to one-haif of its former value. The maximum
current is therefore still kept on the motors, though they may by this
time be running :it lialf'speed. The next contact cuts out the
Fio. 37.— '■ Series-Parallel " Controller.
remuning half, and now the two motors are in " parallel " (_Figs, 3a
and 33), with no resistance in their circuit, both developing a t>ack
E.M.F., which prevents any but the current required to meet the
load from passing through them. The whole operation is completed
and the tramcar running at full speed from rest m a few seconda-
ry GoC^lc
5^ DYNAMO. MOTOR AND SWITCHBOARD CIRCUITS.
The connections of such a controller are given in a diagram designed
by Mr. Tyson Sewell in Fig, 38. (Taken from Tyson Sewell,
" Elements of Electrical Engineering," Crosby Lockwood.) The
diagram is somewhat distorted, the segments being shown in a
horizontal plane instead of one under the other, but this is so
arranged that the connections may be seen more clearly. There is
a small " reversing " switch, which reverses the current in the arma-
tures of both motors, but allows the current to flow in the same
direction in the field-magnet coils. A still further rotation of the
controller handle cuts both motors from the line, and short-circuits
Fig. 38.— Connections oi " Series-Parallel " Controller,
them. They then form a powerful brake. The eflFect of the brake,
however, decreases as the speed decreases, which causes a corre-
sponding decrease in the current, and therefore in the magnetic
braking power. This is only used in cases of emergency, for there
is danger of burning out the motors in so doing, owing to the large
currents induced in them at a high speed, in running as generators
on short circuit. The reversing switch is arranged on a second
vertical spindle beside the first or main controller spindle, and the
two are interlocked so that the motors cannot be reversed except
when the current is off. The two controllers (one at each end of the
car) are connected in parallel; that is to say, similar contacts on the
two are cotmected together, so that when one is switched off and
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 53
locked the car can be controlled from the other. In tracing out the
connections given in the diagram of the " series-parallel " controller,
the row of contacts are supposed to be fixed, while the segments
rotate tc^ether round the central spindle.
Another diagram illustrating a "series-parallel" controller is
given in Fig. 39. It shows clearly the controller spindle with its
contact pieces and stationary fingers. These terminals or fingers
Fir„ 39.— Diagram of " Series-Parallel "
Controller.
are connected with other terminals or fingers placed on a connect-
ing board, which receives wires from the trolley line, the field
magnet coils, and armatures of the two motors, and the series and
shunt -regulating resistances, and by varying the angular position
of the cylinder any desired grouping or modification may bs
obtained.
The various combinations of the resistances and motors which
may be effected by K type of the "series-parallel" controller.
)vGoO'^lc
54 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
manufactured by the British Thomson-Houston Company, are
shown in Fig. 40, from which it will be seen that, when contact is
made on the first notch, the two motors and the whole of the
regulating resbtances are connected in series, with the result that
the starting current is under control. The resistances are then cut
out step by step, and the available voltage at the terminals of the
motors is gradually increased until, at contact 4, the two motors
* Ki «, A, F, A, F,
■^v^Mr^wHrntt-o-mp-o-wsp—
3 cvw\P'w^w^^H>-®w--o--M^^
4 '>WWWWNMWP- 0-Wy--0--W»-
8 'WfP^tmf^vm-o-mr^o^Si^
are simply connected in series across the 500-volt circuit. At this
point, each motor receives and is operated at only half the circuit
voltage; also each motor and its field magnet winding may be
considered as the regulating resistance to the other; also the current
produces approximately the same starting torque as would be
obtained by twice the current, if the motors were connected in
parallel. Notch No. 4 re termed a running point. To further
increase the speed, the field m^net coils are now shunted, and as
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 55
this reduces the magnetic flux, the armatures run at a higher speed
in order to produce the necessary counter or back E.M.F. To
further increase-the speed, the field magnet shunts are cut out; two
thirds of the regulation resistance is inserted in series ag^n. One
motor is then completely shunted, and is finally cut out of action.
The two motors are then finally combined In parallel without any
of the regulating resistances being in circuit. This combination
occurs at contact ii, and each motor operates at 500 volts; also
each motor still takes a normal current. A further increase of
speed is obtained by again shunting the field magnet windings,
whilst the motors are connected in parallel This is shown In No. 12
combination.
With the "series- parallel" controller it is claimed that at
starting there is a saving of 50 per cent, in current by having the
motors in series compared with the current which would be
required if the motors were in parallel for the speed required. The
arrangement also permits a more gradual starting. ■ In Fig. 39,
there Is also shown a reversing barrel or cylinder with its contact
arrangement. The function of the reversing switch is to control
the direction of motion of the car. This reversal of the direction
of rotation of a " series " motor is, as previously stated, brought
about by reversing the direction of the flow of current either in
the armature or field magnet coils (but not in both at the same
time). In practice it is customary to reverse the direction of the
current flowing through the armature when It is desired to reverse
the direction of motion of the car. This is effected by this
" reversing cylinder," due to the requisite combination of the
connections on the reversing cylinder contacts and the contact
springs or fingers.
5.— The Electric Brake.
With electric tramcars it is of the greatest importance to be able
to apply a brake quickly, especially in casesof danger and emergency.
A very efiective kind of braking may be attained by disconnecting
the motor from the mains, and then connecting the armature brushes
with each other through a resistance. When a car is provided with
series motors, a reversal of the " field magnet " connections is
required for getting a braking effect. Assuming the motor to be
)vGoo'^lc
56 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
connected as shown in Fig, 41, the current is flowing in the armature
fromj^. toS., and in the field magnet coils from C. to D, As
previously stated, a back or counter-E, M.F. is produced in the
armature of a motor, which, after disconnecting the motor from the
mains, would tend to produce a current (generated by the rotation
of the armature due to the motion of the car) leaving the armature
at A, and entering it again at B. (Figs. 42 and 43). Hence if, for
Fig. 41. — Series Motor GDnnections.
the purpose of braking the motor, we simply insert a resistance R.
between ^. and D,, then the current will leave thearmature at A.,
flow through the resistance R, then through the field magnet coils
in the direction D. to C. {fig. 42), and enter the armature at B.
Now this arrangement is wrong, because the current is flowing
through the field magnet coils in an opposite direction to what it
did originally. The magnetism of the motor is thus destroyed, no
current i;> produced, and the bratdng effect ceases. To get a braking
(fleet, the armf^tnrv current must flow in the same direction, through
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE.
the field magnet coils, as it did in its original runoing position
(U. from C. to D.) See Fig. 43. By properly arranging the connec-
tions, we can cause the motors to act as generators and to transform
any mechanical energy, due to the momentum of the cari-into
electrical energy, which may be utilised (as afores^d) to produce a
)vGoO'^lc
58 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
powerful braking effect. One method of producing the necessary
changes in the connections is clearly sho<wn in Fig, 44.
B IS comiioueR
^k> WVW-i -O
; " —1 u [gl
-TT-T. K >T-WW , J
6. — Controller and Wiring Diagram of Car Connections
Brush System,
The controller connections and diagrams of the wiring connec-
tions of the system used in the Brush Standard Series -parallel
Controller, with graduated rheostatic brake, are illustrated, in which
Fig. 45 shows the working at each notch of the controller, Fig. 46
)vGoO'^lc
Fig. 45.— Bnisli System of " Series-I^tTallel " Controller.
)vGoo'^lc
60 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
the system of the controller wiring, and Figs. 47 and 48 the system
of car wiring.
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE.
1 i-^m-'mk-wr'^^ fyw^ f ym-
-yWrnr^wMH^- fyw^ j Ow-
'; -%l^-W/WVVAr^Wvk>«-<>-W-
-wHmMm-wAy»-<i'M-
Bmergeiuy
Stop
U>^
K>33^-
7. — Brush Standard H^ System.
In this " series-parallel " controller, fitted with an emergency
brake, Fig, 49 is a diagram of the connections of the working of the
)vGoo'^lc
6* DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
controller at each notch, Fig. 50 Is a diagram of the controller
wiring, and Fig. 51 is a diagram of the complete wiring connections.
In this type of controller, there are three resistances and one
Pig. 50. — Brush H^ Diagram of CoDtroUer Wirii^.
running point with the motors in series, and two resistances and
one running point with the motors in parallel.
8.— Wiring Diagram of the British Engineering Com-
pany's Controller.
Fig. 52 illustrates a wiring diagram of the above company's
H, "series-parallel" controller. It shows the positioning of the
motors very clearly.
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE,
)vGoo'^lc
64 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
9. — ^Wiring Diagrams.
Fig, 53 illustrates a. wiring diagram of a K, controller, and
Fig. 54 illustrates a wiring diagram and controller connections of
Messrs. Dick, Kerr & Co.'s controller, &c. This controller has
seven power and five brake notches.
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE 65
)vGoo'^lc
66 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
AiUomai'K Ctit-oai
4 Speed
Fig. ^<).— Electric Vehicle " $eries-P4rall«l " Controller C^nD^ons,
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 67
10. — Street Car Motors.
The street car motors vary in size and power from about 15 to 50
horse-power each, and run at about 400 to 500 revolutions per
iBai
Forward 1 Backward
43 2 1^12
Fig. 56.— Development of the Controller,
minute, or about three or four times as fast as the car axle. The speed
of the motor is reduced by gearing called " reduction gearing" ; it
consists of a pinion fixed on the motor shaft, which drives a larger
)vGoo'^lc
68 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
gear-wheel mounted upon the car axle. The motor is surrounded
by a gear casing to protect the motors and gears. There is a loss
of power in the use of gears, and so-called " gearless " motors
have been introduced. They run at a speed of about 150 revolutions
per minute, but they are not much used, for practical reasons,
owing to the fact that it is mechanically difficult to suspend them,
and of insulating the armature from the car axle.
II. — ^Accumulator Cars: Electric Vehicles with- Storage
Batteries or Accumulators.
The advantage of the storage battery system is, that each car is
an independent unit ; no accident can cripple a well-organised
system, and the car or vehicle is not restricted to the route of an
electric conductor. The disadvantages are the great weight of the
battery (which is a " dead " weight) and cost of maintenance, also
the lack of reserve power. Then there is the all-important question
of " economy " and efficiency. For the purpose of controlling the
speed of a storage battery car, the cells are grouped into two
separate and distinct batteries. These batteries are connected in
parallel for low speeds, and in ^ries for high speeds. The two
motors may also be connected in series or parallel. The following
combinations are possible. For low speeds the batteries are placed
in parallel, and feed the motors in series, for medium speeds the two
batteries are connected in series and connected to the two motors in
series, and for high speeds the two batteries are grouped in series
and the two motors in parallel. The controllers used to effect these
combinations are similar to a " series-parallel " controller. Such a
method of regulating and the plan <rf connections for an electric
vehicle is shown in Figs. 55 and 56 (pages 65 and 67), in which Ftg. 55
shows the connections at the different Speeds, and Fig. 56 the con-
troller development, showing the connections across the contact strips
of the controller barrel, i and 3 are the armatures of the two motors.
A, AAi, A^ AA„ are the armature connections of motors Nos. i
and 3 respectively, i -|- and a -1-, i - and a -, arethe positive and
negative terminals of the two storage batteries, Nos. i and a.
F. and FF. are the junction terminals of the field magnet coils of
the two motors, i and a. — lis the parallel connection of the field
magnets. R. — RR. is the "brake resistance" coil. It is only in
circuit in the backward positions, and is the electric brake resistance.
)vGoO'^lc
l^^/Tf;
fffoca
'WA
Diq.izeobvGoOi^lc
„Gooi^lc
DIRECT, ALTERNATING AND POLYPHASE. 69
B.S. is an automatic brake cut out. M. is the main "plug" switch
to entirely disconnect the electrical circuit. The " forward " and
" backward " positions show the positions of the controlling handle
or lever of the controller for four speeds forward and two speeds
backward. The developed controller connections clearly explain
the different combinations of the electrical connections for the
various speeds. The round circles numbered 1 to 13 represent the
13 contact brushes which make contact with the contact strips of
the rotating barrel or drum of the controller.
/iain-
Fig. 56B. — Diagram of Connections for Four-pole C. C. Series-wound Motor,
utilised for the purpose of Charging Coke Ovens. Capacity of motor,
34 h.p. ; 500 volts ; 57 amperes. Tramway' Type Coulroller.
)vGoo'^lc
SECTION V.
DIRECT CURRENT PLANTS, etc.
Combined Lighting and Power Schemes, with Batteries,
Boosters, Balancers, &c. ; Direct Current.
z.— End Cell Switch.
In direct current working there are, under cert^ conditions of
supply and demand, great advantages in using secondary or storage
batteries in combination with the generating plant Tlie voltage of
ri^kl<HNlihhHlihl«(i!
End
CeU
Swikh
Lamps
Via. 97.— End Oil Switch.
an"accumulator"(secondary battery) varies considerably between the
points of full charge and discharge voltages. It becomes necessary,
therefore, to be able to vary the voltage of the "accumulator
battery," so that it will work practically in unison with the, gene-
rating plant and source of supply. To secure this variation of E.M.F,
or pressure "end cell" switches are required. Fig. 57 shows a
"storage battery" supplying a two-wire system of distributi<Ml
)vGoO'^lc
DIRECT ALTERNATING AND POLYPHASE. 71
in the circuit of which is p]aced an "end cell " ijwitch. The normal
working pressure of a cell is about 2 volts at charge, which
falls to about I'S volts
at discharge. The " end-
cell " switches are con-
sequently needed to in-
sert or take out of circuit
one or more end cells, so
as to regulate the voltage
of the combined number
of cells which form an
" accumulator battery."
2. — Combined Plant
consisting of Shunt
Dynamo, Storage
Battery, with
Charge and Dis-
charge End Cell
Switches.
Fig. 58 shows the
above combination, in
which we have a "shunt-
wound dynamo," with its
fieldregulator; a "charg-
ing" end cell switch, and
a " discharging " end
cell switch, the whole
supplying a " two-wire"
system, with incandes-
cent lamps in parallel.
3.— Dynamo; Booster
and Battery Con-
nections.
In practice it fre-
quently becomes neces-
sary to raise the voltage above the normal voltage of the dynamo
during the charging of the " accumulator battery," This is done by
Shunt Re^.
■Combined Storage Battery Plant
)vGoo'^lc
7* DYNAMO, MOTOR AND SWITCHBOARD CIKCOITS.
means of A special machine called a " booster. ' (A " booster " is in
reality a dsmamo.) The " booster " is connected in series with the
dynamo by connecting its negative brush with the positive brush of
the dynamo ; the " battery " is connected with the negative pole of the
dynamo and the positive brush of the " booster." The " voltage " can
be raised to an amount equal to the voltage of the "booster" over and
-mm
Fig. 59— Dynamo. Booster and Battery Connections.
above the " voltage " of the supply dynamo. Its range is generally
from volts to about 50 volts. That is, you could raise the " voltage "
of the main dynamo (loo-volt machine) from 100 to 150 volts, and
thus supply the terminals of the battery with any range of voltage
between 100 and 150 volts. The "booster" is generally separately
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 73
excited to prevent any risk of the reversal of its polarity or field
magnetism. The diagram of the connections is shown in Fig. 59.
4. — Regulation of Pressure on the Three-wire System by
means of Balancers (Equalisers).
If the number of lamps on one side of the system is very different
from the number on the other side, the fall of potential on the side
l^i
-^-Ntulmt ,
Kh
9 9 9 P
Vsx'
9
FlQ. Go. — Balancer on Three-wire System.
carrying the larger number of lamps is greater than the ^11 of
pressure on the other side. This defect has been overcome by the
use of the motor generator (called balancer, equaliser, or motor
compensator) in the manner shown in Fig. 60, Here two equal and-
similar motors are placed side by side, their armatures on a common
shaft, and their field m^nets and armatures electrically connected
as follows : —
No. I motor (M,) has its field connected to the high-pressure
mnin and the middle mam, whilst its brushes are connected to the
middle main and the low-pressure main.
No. 2 motor (M.) has its field connected to the middle and
)vGoo'^lc
74 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
low-pressure mains, whilst its armature is connected to the high
pressure and middle mains. If the pressure between the high and
middle mains is lower than the pressure between the middle and low-
piessure mains, the field of No. i motor will be weaker than that of
No. 2 motor, with the result that No. i armature will run faster as
a motor driving No. 2 armature in a stronger field, consequently
raising its back or counter- E.M.F. higher than that of the mains to
which its armature is connected, so that No. 2 acts as a dynamo and
+
FiQ. 61.— Three- wire System mth Balancer.
supplies energy to the more heavily loaded side, thus automatically
regulating &e load, and therefore the pressure.
Fig. 61 illustrates an arrangement somewhat similar, C and C^
are the commutators of the two separate sets of coils wound on the
armature ^., the field f. of which may be connected across the mains
M. + and M. - , coming firom the station bus bars. These mains
are joined up with the outer distributing mains D. + and D. - , and
with one brush of each commutator, the other brushes being
coupled tc^ether and to the balancing distributor d. When the
loads are unequal a similar equalising or balancing takes place as
already described
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 75
5. — Three-wire Distribution with Balancer and Batteries.
If, when the balancer is situated at the generating station, feeders
instead of distributors were connected thereto, the working would
not be satisfactory. In such a case a battery must be used in
conjunction with the equaliser or balancer. In Fig. 62 E. is the
l),„„:b,GOOi^lC
76 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
"equaliser" connected through "end cell" switches with the battery.
The midway points of the balancer and of the battery are connected
t(^ether and with the third- wire or neutral feeder, N. Other " end
cell " switches connect the battery with the bus bars B. + and B. - ,
and with the outer feeders + and — . The pressure may be regulated
on either side by varying the voltage of the battery by means of
these end cell switches.
6, — Three-wire Direct Current System with Storage
Batteries and Boosters.
The diagram of the drcuit connections is shown in Fig, 63, A.
are the ammeters, D. A. are differential ammeters, S. P. D, T.
are single-pole double throw-switches, and, S.P.S.T. are single-pole
single-throw switches. The end cell switches, positive and negative
batteries, and positive and negative boosters are dearly illustrated
in the drawing. Thirty cells on each side of the system are con-
nected to the cell -regulating switches. Four regulating switches are
installed, each having 30 contacts with a current capadty of
2,000 amperes, and are driven by a half-horse power motor, con-
nected by worm gearing to the screw on which the contact brushes
travel. An indicator is connected with these switches by means of
which the last cell on the switch can be read directly from the
indicator on the battery switchboard. The end cell switches are
so arranged that the motors on each pair can be coupled together,
and the two switches operated as one whenever the maximum
discharge rate of the battery is required. Either cell-regulating switch
of each pair can be connected to the main, auxiliary, and the charging
bus bar ; also the booster can be connected between the main and
auxiliary busses. On the panels of the battery switchboard the
following apparatus is mounted in duplicate : one set for each side
of the three-wire system, seven knife switches, one low-reading
voltmeter with 30-point switch to read the voltage of the end cells,
one voltmeter with 5-point switch to read the booster and the
regulating switches, one ammeter for the battery neutral, two
ammeters for the end cell -regulating switches, and the two end cell
switch regulators. The switchboard permits of such combinations
that the battery can be discharged and charged simultaneously, the
former operation at two pressures if desired, or both cell -regulating
switches can be connected to the same bus for maximum discharge.
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE.
„Gooi^lc
78 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
The battery is charged by means of motor-driven boosters, so
arranged that they will maintain a constant speed under the varying
voltage of the busses.
7.— Lighting Plant with Storage Batteries.
In Fig. 64 is shown the switchboard connections of a combined
dynamo and battery system. B. D. L. are battery dynamo lights
' Dynamo BatUry En
Fia. 64. — Lighting Plsnt with Storage Batteries.
B. L. are battery lights, V. S. are the voltmeter switches. The
dynamo is shynt-wound, the voltage of which can be varied by
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE.
79
means of the field rheostat. There are two 15-point, round pattern
end cell switches, E. C. S., one in the charging and one in the
discharging circuit, by means of which the whole battery (60 cells),
or a less number of cells, may be charged and current taken off OD
Fig. 65.— Booster and Storage Battery Plant.
the discharge switch at the normal switchboard voltage. The
switchboard and connections are so designed that the dynamo may
be run to charge the battery or to furnish lights direct, or both
of these operations may be done at the same time. The battery
)vGoO'^lc
So DYNAifO, MOTOR AND SWITCHBOARD CIRCUITS.
may be used in parallel with the dynamos, or the battery may
be used alone.
8. — Booster and Storage Battery Plant.
The diagram of connections is shown in Fig. 65. From the main
board three feeders run to the storage battery switchboard. A
double-throw switch is provided, by which the batteries can be
switched to discharge into the lighting system, or connected to the
dynamos in series with the boosters. The switchboard also com-
prises a differential ammeter and a voltmeter, a ten-point end cell
switch, a booster rheostat, and an underload switch, which breaks
current should the batteries tend to come back on the dynamos.
These instruments are duplicated on each leg of the system. There
is a double-pole, double-throw switch which cuts out the boosters.
The underload switch is very ingenious. It consists of an iron core
pivoted at each end to a horizontal brass support, which is fastened
to a vertical piece of slate. At the ends of the core and at right
angles thereto are secured heavy iron pole pieces. The supports
extend beyond the core, and carry an iron armature, which, when
the switch is closed, completes the magnetic circuit. Around
the core are wound a few turns of heavy wire, with the .ends
bent in such a way that when the switch is closed they dip into
mercury cups, completing the circuit from one main through
the booster and battery back to the neutral. Should the booster
voltage ^1 from a broken belt or other cause, the voltage of the
charging circuit would drop to that of the dynamo, and the con-
sequent reduction in current would allow gravity to act on the
heavy pole pieces of the switch, causing the latter to ^1 and open
the drcuit.
9.— Three-wire, Booster, Battery and Feeder Connec-
tions.
Fig. 66 gives a diagram of the connections of the above. This
diagram shows very clearly the end-cell switches. Twenty of the
end cells on each side of the system are used for regulating. Each of
these cells is separately connected to a contact on the regulating
switches, which carry movable contacts operated by a screw. The
)v Google J
i
DIRECT, ALTERNATING aNI> POLYPMASE.
potential is raised or lowered by cutting in or cutting out regulating
cells. Two regulating switches are connected in multiple on both
the positive and negative sides to permit of a discharge at two
potentials, or to enable the battery to be charged and discharged
Bimultaneously. The booster is used to raise the E.M.F. of the
)vGoo'^lc
8a DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
charging current from the potential of the current supphed to the
installation to that required for charging the battery. The booster
can be used also to raise the E.M.F. of discharge for feeding some
distant point of the system at a higher potential than would be
— BUS
Fig. 67. — Reversible Booster arranged for Ughting Work.
normally required. The machine consists of one positive and one
negative dynamo at each end of a common shaft driven by two
compound wound motors.
10.— Reversible Booster arranged for Lightuig
Work.
A "reversible booster" not only boosts up the supply voltage
to enable a battery to tiecome charged, but also boosts up the
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 83
battery pressure when it is discharging, setting itself automatically
to perform either function, according to the requirements. The
*' Highfield " reversible booster performs the above. In Fig. 67 B. +
and B. — are the bus bars, and D. and D. the dynamos. The
boosting arrangement consists of three machines : a motor, M.,
booster, B., and " opposer " or booster exciter, E. The booster
shunt field coil S, is connected in series with E., which supplies the
exciting current for the former, and the two are joined up to the
ends of the battery. The number of cells in the battery must
be such that at the normal E.M.F. per cell its total E.M.F.
shall be equal to that between the bus bars. The exciter E. is
shunt-wound, and a rheostat, R., enables its excitation to be
adjusted. The motor M. is also shunt-wound, and is connected
across the bus bars. The " booster " armature is connected in
series with the battery. A double-pole throw-over switch, T.O.S.,
enables the booster to be cut out. In addition to the shunt wind-
ing, the booster has also a series winding, St., through which
passes a fraction of the main current flowing into the + feeder,
this fraction being determined by the position of the slide on the
rheostat D. The winding Se. gives a slight boost in the discharge
direction, but this is only appreciable when an extra heavy current
is flowing to the feeder. Thus its purpose is to assist the dis-
charge when the load becomes very great The motor drives the
booster and exciter at a constant speed, and the latter gives a
constant pressure equal to the normal hne voltage. As long as
the battery and exciter voltages are equal there will be no
current in S., and consequently no boost, but directly the bat-
tery pressure falls below that of the exciter the latter acts as a
generator, supplying current through S. to the battery and causing
the booster to give a pressure exactly equal to the difference
between the exciter and battery pressures. The current supplied in
this way by the exciter to the battery never exceeds about five
amperes, and thus plays no appreciable part in the charging of the
battery.
When the battery pressure rises above that of the exciter a
current from the battery will flow through the exciting coil 5. of the
booster, reversing its polarity, and also through the exciter E.,
which will now run as a motor. The boost of B. will then again be
equal to the difference between the exciter and battery pressures,
but in the opposite direction.
)vGoo'^lc
84 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
II. — Reversible Booster as arranged for Traction Work,
The Highfieid reversible booster is also suitable for traction work.
Fig. 68 shows the arrangement. iJ.D.are tlie dynamos, B. B. the
bus bars, M. the motor, E. the exciter, B. the booster, and D, a
rheostat. E. i3 compound wound, and M. is differentially wound, the
speed of the latter being thereby kept more constant. The booster
Trolly Line
B. also has an additional winding, W., in series with the armature,
the function of this being to compensate for Eirmature reactions.
The negative pole of the system is connected to the rails {i.e. to
earth), this being the usual practice, as the effect of electroly^s is
thereby minimised. The field magnais of a reversible booster must be
laminated, in order that when the magfietising current in the shunt
winding is reversed the change of polarity may take place rapidly.
)vGoO'^lc
\ BallrryJ
vz^
Fig. 69,— Kev«rsib1e Booster as arranged (or Tractkm Work.
DiqmzecbvGoO'^lc
86 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
A somewhat more complete combination of the Highfield reversible
booster as arranged for traction work is shown in Fig. 69. Some
of the minor and less important circuit connections are left out,
however, so as to keep the diagram as clear as possible. Still at
the same time it illustrates the more important connections. This
machine is of special construction and design for working in series
with a storage battery, keeping a fluctuating load, as a " tramway "
one, with a practically constant potential, and also the load on the
generator the same. The "booster" armature is always in series
with the " battery," running when the "generator" is running,
and sometimes when the " battery " alone is working the line.
The diagram shows the "booster" driven by a "motor." The
" booster " has laminated fields, excited by a fine wire coil, C. (the
exciter coil), of such proportional resistance that the armature pressure
at a constant speed is similar to the pressure across the "exciter"
coil ends. Any "drop" is corrected by a "series" winding. The
armature leads are connected to the negative terminal of the battery
by " exciter " coil C. So long as the " exciter " and " battery "
pressures are equal, no current will flow in C. ; hence the " booster "
will give no pressure. Should the battery volts rise, a current will
flow in C. proportional to the difference of the "battery" and
"exciter" pressure (which exciter will be motored). The "booster
armature" will then give a pressure equal to the rise of battery
pressure. Should the "battery" pressure drop, the "booster"
will give out a pressure equal to the drop, but will have its poles
reversed, the exciter now running as a generator and giving a
current to the battery. Generally the "exciter" runs as a " motor "
when charging, and as a "generator" when discharging. The
"booster" fields being " laminated," the reversal of the "polarity"
is rapidly made. To increase the pressure as the load on the line
increases, part of the feeder current is shunted round a coil on the
"booster" fields, in such a direction as to "help" the "discharge"
or " oppose " the " charge."
)vGoO'^lc
SECTION VI.
ALTERNATING AND POLYPHASE CURRENTS.
ALTERNATING AND POLYPHASE CURRENTS — POWER TRANSMISSION
SYNCHRONISING — CONTROLLERS PARALLELING OF ALTERNATORS
— TWO AND THREE-PHASE MOTORS AND STARTERS— DEVELOP-
MENT OF MOTOR AND CONTROLLER CIRCUITS, ETC.
I. — "Synchroniser."
In the "paralleling" of alternators the machines have to be
" synchronised." This is done by means of a " synchroniser,"
which may consist of a small transformer, wound with two piimaries
Fig. 70.—" Synchroniser."
and one secondary. The principle of action depends upon the
"mutual induction "between the primary and secondary windings
(Faraday's induction of currents). A "synchroniser" is repre-
sented in Fig. 70, One primary is connected to the bus bars of the
alternating current system, the other primary is connected to the
new machine to be switched in, and the secondary has a lamp in
)vGoo'^lc
88 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
series, as shown. When the speed and voltage of the two machines
are right, if the voltages are not in phase, the effect will be a blinking
of the lamp on the synchroniser. By altering the speed the new
machine is brought into " synchronism," which is shown by the lamp
burning or glowing bright and steady. The machine is then quickly
switched in.
2. — Paralleling of Alternators.
In using alternators for lighting circuits, it is necessary to run
them in parallel with each other, and before this can be done they
must be " synchronised" ; i.e., they must have the same voltage.
Fig. 71. — "Synchronising " Altematora,
same frequency, and be exactly in unison, step, or phase ; i.e.,
the positive and negative alternations of each machine must occur
exactly at the same instant. The method of using a" synt-hroniser"
in connection with the alternators is shown iaFig. 71. The alternator
A,, which is already feeding the main circuit, is shown connected
up by means of a double pole switch to the " omnibus bars " on the
switchboard. This alternator is likewise connected to the primary (Pj)
coil of a small transformer, 7"i (the " synchroniser " is connected as
a '' shunt " to the main circuit), the secondary coil being connected
in series with a lamp and the secondary coil of another transformer,
r,, whose primary coil, P„ is connected up to a second alternator, B.,
which it is now desired to connect up to the "omnibus bar." The
E.M.F. generated at any instant in the two secondary coils due to
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 89
the mutual reaction of the primary coils may be acting either in
unison or opposition. In the former casei the light given out will be
Fic. 73.— Another Method of Collecting ■ Current from &
Two-phase GeDcrator.
a bright light ; in the latter case, a flickering effect will be observed
The machine is switched in when the light is bright and steady,
3.— Polyphase Currents.
In Figs. 72 and 73 are shown two methods of collecting; the current
from two-phase generators. Fig. 72 illustrates a two-phase circuit
DiqmzecbvGoO'^lc
90 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
in which the currents are collected from foui' collecting or slip rings;
Fig, 73 illustrates a two-phase circuit in which the currents are
collected from three collecting or slip rings.
FiQ. 74. — " Triai^ulu " or " Mesh " Connection of a
Thrae-phase Circuit.
Fte. 73.—" Star " Connection of a Three-pbaae Circuit.
Figs. 74 and 75 are examples of three-phase circuits. In each case
there are three collecting or slip rings. In Fig. 74 it will be noticed
that the six free ends of the coils of the generator are connected
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 91
two ends on each slip ring, the external circuit connection forming
■what is known as the " triangular" or "mesh" connection. The
first winding on the generator is connected between slip rings i and
2, the second between slip rings 2 and 3, and the third hietween rings
3 and I.
In Fig. 75, the beginning of each winding is connected to one of
the collecting rings, and the other free ends are brought to a common
Fir,. 76.— "Star "Method of Polyphi
of Power,
junction, this method of winding forming what is known as the " Star"
connection.
4. — Polyphase Transmission of Power,
The methods and connections for the transmission of power from
the generators, as connected in Figs, 74 and 75 to motors, &c., are
illustrated in Figs. 76 and 77. In Fig. 76 this represents the " star "
method of winding and connections. Fig. 77 represents the "mesh "
grouping or method of connecting. In Fig. 76 N. is the common
junction or neutral, the other free ends being connected to the lines
and carried to the motor. The figure shows the " armature " of
the " generator " and the " field coils" of the " motor" con-
nected by three main leads. When the current in j4 . is at its maximum.
)vGoo'^ic
9a DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
then the currents in B. and C. coils are equal, and each is one half
the value of A ., under which circumstances B. and C leads, act as a
return for A. The three sets of coils in the "armature" of the
generator and tha motor field are sometimes joined in series, and
the three junctions connected to the three main leads. This gives
us what is known as the " mesh " grouping or method of winding
(Fig. 77). It will be seen that the " mesh " winding approximates
somewhat to a parallel method of winding when considered with
respect to the external circuit, with the result that the " pressure''
between the mains is less than the equivalent "star" grouping, the
currents being correspondingly heavier. For transmission of power
to great distances, where " low " current strength and correspond-
ingly "high" pressure in the mams is essential, the "star"
^ _I-uu A B
I'lG. 77. — "Mcsb" Mettiod of Polyphase Transmission
of Power.
grouping is preferable. To obtain a given pressure in the mains
with a'Tnesh " grouping requires atx)ut 73 per cent, greater length
of conductor in the armature than with the " star" grouping. There
is the advantage in the " mesh " grouping that, although one set of
windings in the generator or "rotor" may break down, the
machines will continue to run as two-phase machines, whereas with
"star" windings the machines would become simple single-ph&sc
and would not be self-starting. The great advantage of " polyphase
motors" is that they are self-stajting, do not need to run in
" synchronism " (asynchronous), require no slip rings or brushes ;
and polyphase machines in general are specially suitable for the
transmission of power to considerable distances, where a "high
pressure on the line is essential" to economy as regards weight
of copper.
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 93
TRANSHrSSION OP MuLTlPHASE CURRENTS.
5. — Two-phase Transmission with Four Wires.
Power may be transmitted by polyphase current in a variety of
methods as regards the number of mains, such, for example, as power
transmitted betweena generator and a motor. Two currents produced
in a two-phase generator may be separately conducted by means of
Fig. 78,— Two-phase TiaoEmUsioa with Four Wires
Fig. 79.— Two-phase Transmission with Three Wires.
two pairs of wires to a two- phase motor. In this case, four m ai n s
are required, as shown la Fig. 78. The windings i and 2 indicate
the first and second phase windings on the generator and motor.
6. — Two-phase Transmission with Three Wires.
We can, however, combine two of the mains into one main, say
A.B. and CD, In this arrangement (see Fig. 79) each phase has
)vGoo'^lc
94 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
one main for itself, but the middle main is common to both phases.
This middle main is the common or return main for the two currents
flowing in the two outer mains. The sectional area of the middle
wire must be about i^ times that of either outside wire, because the
resultant value of these two component currents is about i'4i times
the value of each taken separately.
7.— Three-phase Vranamission with Six Wires.
With three-phase transmisaon we may lead six wires from the
generator to the motor. The three-phase windings are indicated by
1, 3, and 3 in Fig. 80.
Fig. So.~Tbiee-phase Transmission with Six Wires.
8. — Three-phase Transmission: "Star" connected with
Four Mains.
We can combine the returns, connecting the inner ends of the
generator and motor returns together to form one common return.
We thus get three single leads and one common return, as shown in
Fig. 81. When the phase voltage is 100, the voltage between the
outer terminals is 173, and between any outer and return is 100
volts.
g. — Three-phase Transmission: "Star" connected with
Three Wires.
In Fig. 82 is shown the arrangement with three wires only, dis-
pensing with the common return. The common return wire is not
necessary when the generator is only supplying power for motors.
Between any two of these mains the voltage is equaL
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 95
xo.— Three-phase Transmission : Mesh Connection wftb
Three Wires.
Fig. 77 illustrates the " mesh ". or " delta " connection. The
voltage between the outer mains is equal to the phase voltage.
Assuming that in these several cases the "phase voltage" is
100 and the " phase " current is 100 amperes, we find in the
Fig. 81.— Three-phase Tronsmissiou "Star" connected with Four Wires.
Fia. 8a.— Three-pha$e Transmission "Star" conaected with Three Wires.
"mesh" connection that the*'voItage"between the outer mains is
"equal" to the " phase voltage," but the" current" in the outer
mains is 1-73 times the " phase current."
With the " star " connection the " voltage " between the outer
mains is 1-73 times the " phase voltage," but the current in the
outer mains is equal to the phase current.
)vGoO'^lc
g'J DYNAMO MOTOR AND SWITCHBOARD CIRCUITS.
Single-phase Circuits: Effect of Self-ii
AS REGARDS PtlASE DIFFERENCE.
II.— Starting of " Single- phase " Motors with Self-induc-
tion in an AuKiliary Circuit.
We can cause a "single-phase motor" to become "self-
starting" if we supply it during starting with a second - phase
current, which differs in relative phase with the m^n phase current.
This condition can be attained by inserting in a branch "auxiliary"
Fir>, 8y — " Phase-difference " Method of Starting " Single-phase " Motors
by means of Self-induction inserted in Circuit.
drcuit a choking-coil which possesses self-induction. The
arrangement is shown in Fig, 83. The "main" phase is con-
nected directly to the mains , the " auxiliary " phase, which is a
branch of the main circuit, is in series with achoking-coil. This
produces a " lagging effect " (due to self-induction), and likewise
a "phase-difference." This gives the required condition to
cause the motor to be self-starting: The eingle-phase motor
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 97
cannot, howevefi start under full load, but with only a part of its full
normal load.
i3.~-Starting of ** Single-phase" Motors with Capacity io
an Auxiliary Circuit.
As we have jost seen, we can cause a " phase difference " by
utilising "self-induction" effects; likewise we can cause a phase
difference by inserting " capacity" in an " auxiliary " circuit.
The arrangement is shown in Fig. 84. As in the previous case, the
Flo. 84. — " Pbase-diflerence " Method of Starting " Single-phaae " Motor*
by means of Capacity inserted in the Circait
-' auxiliary "circuit is a branch to the " main " circuit In the
"auxiliary" circuit is inserted a condenser. This produces a
**leading effect" and likewise a "phase difference," conse-
quently the desired conditions.
Sometimes the effects of both induction and capacity are
employed for starting a " single-phase " motor, a " choking-
coil" being inserted in one circuit and a "condenser" in the
other. We can also produce a phase difference by inserting
'* ohmic " resistance in one winding.
)vGoO'^lc
9" DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS
13. — Reversal of Alternating Current Motors, Single-
phase.
When there is no auxiliary phase in circuit no change of connec-
tions is necessary, because it has no tendency to turn in one direction
in preference to the other. It all depends on which direction it is
rotated mechanically before the current is switched on. A "single-
phase ' ' induction motor with an " auxiliary " phase circuit behaves
Fic. 85. — Metboa ol Connections, so as to cause a Reversal of tbe
Directioa ol Rotation of a " Single-phase " Motor.
like a "two-phase "motor. Figs, 83, 85, and 86 illustrate respec-
tively the method of connecting the several terminals so as to get a
clockwise rotation and a counter-clockwise rotatioa There are
shown two methods to get the counter-clockwise rotation. One is
to alter the connections of the main phase (Fig, 85), and the other
is to alter the connections of the auxiliary phase {Fig. 86).
With a "three-phase" motor the reversal of rotation may be
effected by changing the ends of any two of the three mains fed by
the alternating currents.
)vGoO'^lc
DIRECT ALTERNATING AND POLYPHASE. 99
B
. 86.— Another Method of Connections, so &s to cause a. Reversal
of the Direction of Rot&tioD of a " Single-phaae " Motor.
1 f \ j p
Fic. 87.— Method of Operating a " Three-phase" Motor on a " Singie-phaaa"
Current Supply,
14. — Method of Operating a Three-phase Motor on &
Single-phase Current Supply.
In Fig. 87 M. is a three-phase motor, R. a non-inductive resistance,
C. self-induction coil ; S. and Sj are switches.
The motor M has the usual field winding, and a *' three-phase '*
)vGoO'^lc
lOO DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
winding on its "rotor." The "stator" !s connected as shown,
la the "primary" of the transformer is connected a "non-
inductive" resistance, R., and a self-induction coit, C. By
means of the switches S. and S^ these can be put in and out of cir-
cuit. At starting they are put in circuit and produce a sufficient
displacement of " phase " to start the motor. After the motor has
Started and attained speed, the snitches S. and S, are opened, and the
/ 2
Fig. 88.— Rotary Converter and Tranaformer, PoljrpIiMe
Connections. Two-phase Method.
reaction of the three-phase winding on the " rotor " induces a
current in X.Y.Z. of the " stator" winding, the machine continuing
to run as a three-phase motor, although supplied with single-
phase current. The " stator " is connected as shown to the two
ends and middle point of the secondary circuit of an ordinary split
transformer;
15, — Rotary Converter and Transformer Polyphase Con-
nections, Two-phase, Three-phase, and Six-phase.
We can connect converters and transformers by different methods
on two-phase, three-phase, and six-phase, circuits. In
Fig. 88 is shown a two-phase arrangement. In Figs, 89, go,
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE.
3 -»mm^ 2
Fill. 89.— Rotary Converter and Transformer, Polyphase
Connections. Three-phase Method.
*wvvvwyvvvvvvy vyvw'rtwvirt'yww vwvwvyvvwvw
Fig. 90.— Rolar; Converter and Transformer, Polyphase
Connections. Three-phase, a Second Method.
)vGoo'^lc
loa DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
and 91 are shown three different methods of connecting three-phase
circuits, and in Figs. 9a, 93, 94, 95, are shown four different methods
vwwwwvwvv
2\ 3
Fig. 91.— Rotary Converter and Transformer, Polyphase
Coimeclions. Three-phase, a Third Method,
Fig. 91.— Rotary Converter and Transformer, Polyphase
Connections. Six-phase Method.
g™o::b,GoO'^lc
3_3_
l^/V'^^/vvvvv^_-A'vvvvvvvv'v_/wvvvvwwN
^vvv<yvvw| yvvvvvvvvv^ avwvwvw
Fig. 93. — Rotary Converter and Transformer, Polypbase
Connections. Six-pbase, a Second Method.
VWWWWM^VVVW V»PWi»%PVVWli«.WV*Wf Vir>Wrt(WWVW*VVV*
Wa/vvwv\ "wwyvvvvv Wa/WWV\£-
Fig. 94. — Itota'j Converter and Transformer, Polyphas
Connections. Six-pbase, a Tliird Method.
DiqmzecbvGoO'^lc
I04 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
of connecting up six-phase circuits. The connections explain
themselves, and can be easily traced by means of the numerical
numbers.
i6. — Three-phase Distribution for Power and Lighting.
The advantage of the three-phase system of distribution for lighting
.■Mid power work lies in the fact that it can be economically used for
■vwwvvvw'rtn'vv"
^ 1
|JL_^VVVSA/VVWWWVV wvvvvvvvvvvvvv\:i_
Fio. 9j. — Rotary Converter and Transformer, Polyphjue
ConDeclions. SU-phase, a Fourth Method
tmasmis^on over considerable distances ; and thus a central «tation
can do a large amount of business by supplying power to the out-
lying factories and mills, and in the supply of small lighting plants
in the outlying districts. Another advantage lies in the fact that
rotary converters can be operated. Also direct current for tramways
or light railways can be produced, or direct currents may be required
for lifts, hoists, &c., or for electrolytic work. The disadvantage ol
the two-phase system as compared with the three-phase, taking first
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 105
the two-phase three-wire system, 15 that for a definite amount of
power to be transmitted at a definite pressure with a given loss, the
amount of copper is considerably in excess of that required for the
three-phase system under the same conditions ; and, moreover, the
system on inductive load is very difficult, if not practically impossible,
to operate. The two-phase four- wire system possesses similar disad-
vantages to the two-phase three-wire as regards copper, but for
transmission purposes solely is fairly satisfactory, while on inductive
load the operation is difficult. It will be seen that such a system
must be divided into groups or sets of groups, this division naturally
overcoming many advantages, and, moreover, it becomes necessary
1 3 control each group by means of an induction regulator, as the load
tjmv
Fig. 96.— "Star" Method of Three-phasa Distribotion for
Power and lighting.
factor of the various groups may be entirely different, owing to the
peculiarities of the different neighbourhoods into which the groups
run. Consequently to keep constant pressure adjustments on each
group requires careful attention. A three-phase generator is capable
of taking 75 per cent, of its rated capacity on one phase with normal
heating, and this single-phase load is to all intents and purposes as
great as that which could be carried by a machine of equal weight
and cost, if it had been designed for single-phase work. If the
generator is connected " star" feshion, and is used as a single-phase
machine, two-thirds of the windings are active, and the pb.cing of
these active coils is practically the same as would be arranged for,
assuming the machine to be designed for single-phase working. In the
first system of three-phase distribution for power and lighting the
generators are connected " star" f;ishion with a fourth wire, taken
from the neutral point N. (see Fig. 9G). In this system the potential
)vGoo'^lc
iiG DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
between the line wires is 4,000 volts, and between any line wire and
neutral is 3,300 volts. From the station three-phase feeders are run
» 8
m
Fig. 97.— Low tension Three-phase System for Power and L^hting.
iD
■""
Termiiab
Fig. 98.— Low-tension Distribution by the Single-phase Thiee-wiie System.
from which a three-phase network of 4,000 volts is run, so that con-
sumers may be connected by short single-phfice branches tapped ofF
from one outside wire and the neutral. The necessary transformation is
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE.
107
done by means of an ordinary transEormer wound for 2,300 volts
primary, and the required voltage on the secondary. \ . lien " motors "
are required to ha operated they may bf run from the three-phase
mains, a three-phase transformer being used, which is a very good
balancer. This system can be worked so that the motors can be
operated with practically no effect on the lighting. It will be noticed
that the feeders can be switched on to either of the three main wires
and the neutral as shown at A . and B.
In Fig. 97 is illustrated a low-tension three-phase system (four-
wire), The primaries of the transformers ate connected " delta "
K^
K^
•V c /
~\2 C"
\ "
Fig. 99.— Sii^le-phase Alternators .n Parallel
^ishion, while the secondaries are connected "star" ^hion, the
neutral being connected to the common connection, and the lights
being connected between one of the outside wires and the neutral
wire ; these are balanced as nearly as possible, while motors are con-
nected to ' delta " connected transformers across the three line wires.
A third system {Fig. 98) is that of a low-tension distribution by the
single-phase three- wire system, taken from one side of a three-phase
generator.
17.— Working of Alternators in Parallel.
In Fig. 99 ia shown the connections of two 2,000 volt single-phase
alternators with transformers used to reduce the E.M.F. to ioovoli3
)vGoo'^lc
io8 DYNAMO. MOTOR AND SWITCHBOARD CIRCUITS.
for the synchronising lamps, A. and B. represent the machines, C.
and D. the main switches, £. and F. the transformers, L. the synchro-
nising lamps, and P.P. the pilot tamps. The transformer connections
should be right. To synchronise follow out previous instructions,
when the lamps L. will bum bright and steady, and the pilot lamps
P.P. wiU be dark.
Fig. loo shows the connections of transformers and synchronising
lamps sometimes used for starting synchronous motors or rotary
Dfmmo
•Synchronous f
IJtj
VWVWN >vwwv\
Fio. 100.— Method of starling Synchronous Motors or
Rotvy CoDverten,
converters. With this method of connection, however, it b neces-
sary to have an additional switch to entirely open the circuit between
the two machines, and the traoefonners are useless for any other
purpose but synchronising.
In connecting two-phase generators for parallel running it is
necessary to synchioiuse both phases the first time the marhines are
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. log
paralleled. After they have once been*' phased-up"syDchroni^g
one phase is sufficient. Fig. loi shows the connections for properly
" phasing up " two two-phase generators, where A. and B. represent
the generators, C. and D. the four-pole m£un switches, E., P., G., H. the
transformers, and LX. the synchronising lamps. To synchronise, if
the machines are running at full speed and voltage, close switch C. :
the lamps will flicker ; then open switch C. and close switch D. to see
if transformers are rightly connected. Then open switch D. and close
Fig, ioi.— ParalleliTig Two " Two-pbase " Generators.
switch C, ; lamps L. and L' ought to glow brightly in unison. If
one is bright while the other is dark the phases are connected
wrong, and the lead wires of one phase on one machine should be
reversed. Then test out synchronising apparatus as at first ; if all
the lamps glow in unison the machines may be thrown together
without danger. The synchronising apparatus may then be
removed from one of the phases, and the leads of the remaining
. transformer on machine A. transferred to the other side of the
switch C.
)vGoo'^lc
no DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
Fig. 102 shows the coDDections of synchronising lamps and
transformers for paralleling two " three-phase " machines. To
synchronise, proceed as in the case of the two-phase machines.
If the lights on both phases do not come and go simultaneously
when the machines are running at normal voltage, reverse two
leads on one machine and try again. The right combination will
readily be found. It is only necessary to "phase-up" two of
the phases and the third will be right. After the machines have
—Paralleling Two ' ' Three-phase ' ' Generators.
once been paralleled, and the leads connected to the switchboard,
synchronising one phase is sufficient, as in the case of the two-phase
machine.
i8. — Canal Haulage by Means of Electricity,
In the case of long canals, the power would be transmitted on the
"three-phase" alternating current system at high pressure
and at suitable points would be transformed down by means of
stationary " three-phase transformers " and " rotary con-
verters" to low-pressure direct current. Fig. 103 explains the
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. iii
method. G is the three-phase generator, H.PJ^. are high-pressure
feeders, T. are the transformers (three-phase), R.C. are rotary
converters, C. is the electrical conductor, L. is the aerial railway
line, which is bonded at intervals ; to these bonds B.BJB, are
Fio, 103. — Transformer and Rotary Converters for
Canai Haulage,
r' connected one of tlio terminals of the direct current portion of the
rotary converters R-C, which aerial line forms a return conductor
of very low resistance. The voltage adopted for the transmission
of the power would depend upon the length of the line and the
position of the generating station — in all probability from a,ooo to
$,000 volts.
)vGoO'^lc
na DYNAMO. MOTOR AND SWITCHBOARD CIRCUITS.
19. — Single-phase Pumping Plant.
Single-phase motors may be utilised for pumping purposes.
Fig. 104 illustrates the diagram of connections of the pumping plant
as installed by the Hammersmith Vestry. The pumping plant consists
of two single-phase motors of about 37 B.H.P. Each motor is
fed by a separate 30 kilowatt transformer, which transforms the
primary current of 2,200 volts and 50 cycles to a pressure of 220
volts, for which the motors are designed. The transformers are
Connected by concentric cables to a high-pressure fuse-board of
the "Ferranti" standard oil brake type, the feeder between this
and the power-house being a. paper insulated, lead-covered, con-
centric cable, having its outer earthed ; this can be plugged on to
either transformer or to both at the fuse-board. The low-pressure
switchboard, made by Messrs. Witting Bros., consists of two inde-
pendent white marble panels, each containing an ammeter, a
double-pole switch and a fuse, a voltmeter being common to both
panels ; these panels also contain the starting resistances and
multiple contact switches X.X. for the rotor circuits of the motors.
It will be seen from the connections that everything is in duplicate,
each motor pump, with its transformer and switchgear, being inde-
pendent and in parallel, so that a risk of total failure of condensing
water is very remote. The motors are of Messrs. Witting Bros.'
standard induction type, and are directly coupled to the pumps, do
clutches being used. A special feature of these motors are their
large starting torques and overload capacities, combined with good
efficiency and high-power factor. A non-inductive rotor resistance
is used at starting, which is inserted into the (star -connected) rotor
windings through the intermediary of slip-rings and brushes ; the
latter are of laminated brass, while the slip-rings are of steel. A
small auxiliary resistance is used in series with the running phase
at starting; this is short circuited automatically by the auxiliary
switch, which cuts out the starting phase when the speed has
attained a certain value. As can be seen from the diagram of con-
nections, this auxiliary switch, although electrically insulated from
the hand-wheel and the three-way switch which cuts out the rotor
resistances, is actuated mechanically by a projection from the hand-
wheel, SO that the motor is started simply by slowly turning the
hand-wheel in one direction. The " stator" coils are arranged in
a six-pole grouping, which gives a speed of 1,000 revolutions per
minute at no load. The "stator" windings are buried in slots
)vGoO'^lc
blRECT, ALTERhlATItiG AND POLYPHASE
Conaatrie h'talen.
gJ'^agJ
Starting Resislaaa, combined with Svitdtfor Auxmoff
Pfioii and Mai" Phast Resislanet.
Fig. 104. — Single-phase Pumping Plant.
)vGoo'^lc
ii4 MNAMd, MOTdk Aiib SWitCiiBdARD ciRCOlTS.
insulated with micanite troughs, and as the three-phase "rotor" is
wound in a similar way, the windings being keyed in by means of
fibre wet^es, these motors are practically indestructible.
ao.— Practical Working of Rotary Converters.
Fig. 105 illustrates the diagram of connections with a " rotary
converter," utilised on a three-phase circuit, also the neces-
WJSubm ihil
Pig, 105.— Eolary Converter on Three-pbase Circuit
sary apparatus is shown which is qualified in the drawing. This
illustrates the great flexibility of the "rotary converter" when
employed in a combined alternating and continuous current station;
it is, of course, well understood that a " rotary converter " is
reversible in its action, and can be employed for converting either
)vGoO'^lc
>litg Sedian SwiltAts
Fio. loG.—Polypliase Machinery Connectiona,
DiqmzecbvGoO'^lc
ii6 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
from altematiDg (single and polyphase) to direct current, and from
direct to alternating. By the above arrangement the " rotary
converter" can be used for running as a direct-current generator
in parallel with one of the direct-current sets, being driven by a
three-phase alternator, or for generating alternating current ia the
event of the alternator being shut down, and also for runtUDg In
parallel with the alternator in times of excessive load,
31. — Polyphase Machinery.
Fig. iq6 illustrates the diagrams of connections required for a
three-phase generator driven both by a gas engine and a steam
engine. When connecting the gas-driven generator to the " bus "
bars supplied by the steam-driven generators, a choking coil and
an artiiicial load are used. The latter does not consist of a resist-
ance connected to the generator, but of a special eddy-current brake
acting on the fly-wheel, having a maximum braking effect of about
300 H.P. For work of this character, an artificial load is an
absolute necessity, as an unloaded gas generator cannot be brought
up to speed and thrown on the bus bars. The brake in question
only absorbs a trifling amount of energy from the direct current
mains, requires no additional space, can be regulated with ease and
accuracy, and is an excellent mechanical job. Both the brake and
the choking coil are put out of use as soon as the gas generator is
working on the load ; the (three-phase) choking coil is adjustable,
and its function is simply to hmit the synchronising currents which
occur during the adjustments.
23.— Alternating Current Switchboard Connections at
Hastings.
In Figs. 107 and 108 are shown two very ingenious systems of
switchboard connections. Fig. 107 ia the diagram of the main
switchboard connections ; the main switches controlling all the brush
machines are of the water break type, but a horn break type of
switch is used for controlling the turbo-alternator. No fuses or
excess current cut-outs are used between the generators and the
main bus bars. It is contended by some designers that no
automatic device is necessary between modern alternating current-
generators and the bus bars, as a faulty generator may be cut
)vGoo'^lc
DJRECT, ALTERNATING AND POYLPHASE. 117
out of circuit by the attendant in charge. This would be true if
something corresponding to the central zero ammeter in continuous
current stations could be obtained to indicate which generator was
failing, but it usually happens that, when one of the generators fails,
all the ammeters go hard over to their maximum reading, and the
attendant may have nothing to guide him as to which generator
has failed. In the United States this difEculty has been overcome
by using a return current relay to close a local circuit through an
indicating lamp, fixed directly over the operating switch controlling
the failing generator. At Hastings, instead of the delicate relay
Fig. 107. — Alternating; Current Switchboard Connections.
referred to, a small series transformer is inserted in the main circuit.
This transformer is wound with two secondaries, and incandescent
lamps, coloured red and green, are connected respectively across
each secondary. The construction of the transformer is such, that
when the generator is doing useful work the green lamp is lighted ;
but should the generator fail and receive current from the bus bars,
the green lamp is extinguished and the red lamp lighted. There are
no moving parts in connection with this most interesting and
ingenious device, and consequently its behaviour is absolutely
reliable. G.G.G. are the generators; A■^,At,A^, water break
switches; B^,B^,B^, two-way switches; C. two-way water break
)vGoo'^lc
ii8 DYNAMO, MOTOR ANii SWITCHBOARD CIRCUITS.
switch; Df,D„D^, two-way feeder switches; E^.E^E^, feeder
fuses; X^,Xt,X^ red lamps; Y■^,Yi,Y^ green lamps.
Fig. 108 is a diagram of the Sub-station Connections. A, Aj,
are high-pressure feeders; B. discrlmlDating choking coil; C,C],
Fig. ioS.— Alternating Current Sub-station Connccli
disconnecting switches, D. discriminating transformer; E. high-
pressure bus bars; F,Fj,F,, high-pressure fuses; G,Gj,Gt
transformers; H,Hj, low-pressure discriminating cut-outs; 1. 1.,
low-pressure bus bars; J,Ji, main ammeters; K. watt-hour
meter; L. double-pole main switch; M,Mj, M„ distributing
bus bars; N,N,, fuses. Each sub-station is fed by two
independent high-pressure feeders in duplicate. By the above
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. ng
arrangement, the liability of a failure on one feeder causing a break-
down on the other feeder has been entirely obviated, as an excessive
current is prevented from flowing from one feeder to the other
without any form of switching device whatever. For this purpose
the feeders at the distributing station end are connected together
throv^h a choking coil, consisting of a few turns of insulated copper
wire wound on an iron core The supply of the load on the sub-
station is tapped off from the centre of this winding. Under normal
conditions, the current being supplied to the sub-station is divided
equally between the two feeders, and its tendency is to magnetise
the iron in opposite directions ; as the two magnetising forces just
neutralise each other, there will be no magnetism in the core, and
consequently no inductive drop in the windings. Should one of
the feeders break down, current will tend to return towards the
fault from the healthy feeder, but this current will circulate round
the core of the discriminating choking coil in one direction only.
As a consequence the core will at once become magnetised, and the
counter electromotive force, induced in the coil, will entirely prevent
an excessive current flowing from the healthy feeder to the faulty
feeder. Providing there is a short circuit, it is desirable that the
feeder should be disconnected as soon as possible. This may be
very simply effected by means of the discriminating transformer D.
The secondaries are, in this case, short-circuited by copper fuse wires,
which support the wdghted levers that serve, when released, to dis-
connect the respective feeders from the choking coil. The high-
pressure primary of this transformer is connected between the
duplicate feeders. It will be obvious that under normal conditions
there will be no difference of potential between the terminals of this
winding, but should a feeder fail, current will flow from the healthy
feeder to the faulty feeder through the primary winding of this
transformer, and the construction of the transformer is such that
a heavy current will be induced only in one of the secondary wind-
ings, namely, that which controls the switch in circuit with the
faulty feeder.
23. — Application of Polyphase Currents to Electric
Traction.
The method of adopting polyphase currents (through the inter-
mediary of three-phase rotary converters) to the retjuirements o(
)vGoo'^lc
I30 DYNAMO. MOTOR AND SWITCHBOARD CIRCUITS.
modem electric trac-
tion, is shown, diagram-
matically, in essentials
in Fig. 109 (taken from
Tyson Sewells " Ele-
ments of Electrical
Engineering," Crosby
Lockwood). The illus-
tration needs but littls
explanation, ^.repre-
sents a three - phase
alternator, generating
at say 5,000 volts.
T. T. T. are three-phase
transformers, or three
single - phase trans-
formers, one on each
phase, in sub-stations
along the line, which
transform down to
about 300 volts. R. C.
represent rotary con-
verters, converting
from three - phase to
direct current at 500
volts. F. F. are feeders
supplying direct cur-
rent to the line or third
rail, which is divided
into sections. The cur-
rent returns by the
track rails, which are
electrically connected
or " bonded " by stout
copper rail bonds, and
these are connected to
the negative bus bars
at intervals.
)vGoO'^lc
DIRECT, ALTJ-RNAJING AND POLYPHASE. lai
34.— Paralleling of Alternators.
In the synchronising of alternators by the aid of lamps, in some
instances (more general in the United States) it is the custom to
switch in the alternators when the indicating lamps are out or dark,
iJUsBar
Phase x /"x
Fig. 110. — ParalleliDg of Alternators. In Phase, Lamps i[
Phase V ^--^
lamps X^J\
/llttmatvrf /llttmatBr Z
Fig. III.— Paralleling of A1terDalor& la Phase, Lamps oul.
and in other cases (more general in Great Britain) the alternators
are switched in circuit when the lamps are in or burning brightly.
In the first case, the synchronising transformer secondaries (the
lamps are inserted in this circuit) have to be connected in opposi-
tion, whilst in the latter case they are joined so as to act in unison.
)vGoO'^lc
133 DYNAMO, MOTOR, AND SWITCHBOARD CIRCUITS.
SI
if
8.1
„Gooi^lc
DIRECT, ALTERNATING AND POLYPHASE. 123
The outline circuit diagram of connecting the primaries ?jid
secondflries of the transformers to the main circuit is shown in
Figs, no and in.
The alternator bus-bars, primary and secondary circuits of the
Fig. 113.— Motor on Two-pbase Foner Sapply. Thir^ H.P. aoo volte, per phase.
transformers T,, and phase lamps (two in series) are clearly shown.
The method of " paralleling " in both cases is as described else-
where ; the only difference is, in one case the machines are paralleled
with lamps " out," and in the other case with lamps " in."
)vGoo'^lc
124 DYNAMO, MOTOR, AtJD SWITCHBOARD CIRCUITS.
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 125
35. — Three-phase Motor Starting Resistance.
Fig, 1 14 represents the " rotor " slip rings with brushes of a three-
phase motor, and 5. R. its starting resistance. When in the extreme
left-hand position the resistance is out of circuit and likewise the
" rotor."
To start the " rotor " of the motor, the current is first switched on
to the "stator" circuit by means of an ordinary three-pole switch
Fia. iij. — Three-phase Motor with Controller.
connected to the three-phase feeders. The handle H, of the " rotor
starting resistance " is now pushed over on to the contacts X. X. X.,
which places all the resistanci of the three separate sections in
circuit with the respective three-phase windings of the " rotor."
The " rotor " now starts under load, and the switch handle on being
further revolved in a right-handed direction as shown reaches the
final contact studs Y. Y. Y., in which position all of the resistance is
cut out of circuit, thus short-circuiting the rotor winding, and the
)vGoo'^lc
186 DYNAMO, MOTOR AND SWITCHBOARD URCUliS.
motor now exerts its greatest torque. It will be noticed that the
starting resistance is not placed in the main feeder circuit, but only
in the " rotor " circuit (which is acted upon inductively by the three-
_„ _ Seeondtrf Cfl-ndtr
Fig. 116. -Wiring Di^jram and Development of Controller.
phase current in the " stator," which itself is directly connected to
the three-phase feeders). This resistance is necessary at starting
for the purpose of allowing the " motor " to start under load.
To reverse the direction of rotation, interchange any pair of heads
connected to the feeders.
)vGoO'^lc
„Gooi^lc
„Gooi^lc
SECTION VII.
CENTRAL AND POWER STATION LAYOUT AND
OPERATION.
DIRECT AND ALTERNATING CURRENT SWITCHBOARDS — TEST PANELS —
TRACTION SWITCHBOARD THREE-PHASE SYNCHRONISING GEAR —
BOOSTER AND BATTERY CIRCUITS — COMBINED LIGHTING AND
TRACTION SWITCHBOARDS— MANIPULATION AND OPERATION OF
STATION — AND POWER HOUSE PLANT AND APPARATUS.
1.— Fault Test Panel.
The accompanying outline diagram shows an arrangemeat of a
fault test panel sometimes used on a 460 to 500 volt between the
outers on a direct current circuit.
References to the iigure : — F^, F„ F, are 100 ampere magnetic
blow-out fuses. A., B., C. and D. are 100 ampere quick-break
switches. ^1 is an ammeter which has a range of reading o to 10
amperes. A^ is an ammeter which reads from o to 3*5 amperes.
F, is a 5-ampere magnetic blow-out fuse. L. is an 8 cp. lamp,
230 volts.
Normal position of switches: — A., open; B., closed; C, open;
D., open. If a positive or negative cable fault occurs, the fuse F,
blows, and the lamp L. lights. The tests are made daily. When
testing the positive, n^ative, and neutral feeders, alt the switches
are opened.
Positive faults : — If there is a fault on the positive feeder, on
closing B. or A. the fuse F, will blow and light lamp L. If this
occurs, close switch, D. ; this short-circuits lamp L. and ammeter
A,. The reading will be indicated on ammeter A^
Negative faults: — If there is a fault on the negative cable, on
closing either B. or C, the fuse Fj will blow and the lamp L. will
light. If this occurs, close D., which short-circuits L. and ammeter
i4,. The reading will be shown on A,,
)vGoo'^lc
138 DYNAMO, MOTOR AND SWrTCHBOARD CIRCUITS.
Neutral faults ;~If there is a neutral feeder fault, the same result
occurs as with the + or — .
Note.— In testing for positive (+) or negative (— ) faults the
—Bus -Bar
Fig. ii8,— Fault Test Fanel.
reading of the ammeter will be different according as B. or C„
A. or B., respectively, are closed, for the volts in one case ei^uals
230 volts, while in the other case they equal 460, i^„ half voltage of
outside mains between neutral and either outer.
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 129
3. — Traction Switchboard Circuit Connections.
Fig. 119 illustrates an outline diagram of the above, in which
M.G.S. = main generator switch; M.C.B. = main circuit breaker;
C.B. = section circuit breaker ; K.S. = knife switch ; W.M. =
watt-meter ; R. = resistance for watt-meter ; L.A, = lightning
arrester.
C. = choking or kicking coil ; F„ F,, F, are the separate traction
circuit feeders connected to the trolley wires of the different routes,
© ©
of Connectors for Traction Switchboard
they being connected to the positive bus-bars. Vm. = bus-bar
voltmeter; A. = the feeder circuit ammeters connected across the
shunts S. The rail earth returns are connected to the negative bus-
bars. The lightning arresters L.A. are connected to earth.
The Board of Trade Regulation Na 5, appertaining to the testing
of electric tramway circuits and connections, provides in the testing
of earth connections that " they shall be constructed, laid, and
maintained so as to secure good electrical contact with the general
mass of earth, and so that an electro-motive force not exceeding four
volts shall suffice to produce a current of at least two amperes from
)vGoo'^lc
130 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
one earth connection to the other through the earth, and a test shall
be made at least once in every month to ascertain whether this
requirement is compHed with,"
Regulation No- 6 provides "that the current passing from the
earth connections through the indicator to the generator shall not
at any time exceed either two amperes per mile of single tramway,
or five per cent of the total current output of the station ; and, in
order to provide a continuous indication that this condition is com-
plied with, the corporation or company shall place in a conspicuous
position a suitable, properly connected, and correctly marked current
indicator, and shall keep it connected during the whole time that the
line is charged."
Regulation No. 7 provides that, "when the return Is partly or
entirely uninsulated, a continuous record shall be kept of the differ-
ence of potential during the working of the tramway between points
on the insulated return. If at any time such difference of potential
between any two points exceeds the limit of seven volts, they shall
take immediate steps to reduce it below that limit."
Regulation 10 provides that " the insulation of the line and of the
return when insulated, and of all feeders and other conductors, shall
be so maintained that the leakage current shall not exceed one-
hundredth of an ampere per mile of tramway. The leakage current
shall be ascertained daily before or after the hours of running when
the line is fully charged. If at any time it should be found that the
leakage current exceeds one-half of an ampere per mile of tramway,
the leak shall be localised and removed as soon as practicable, and
the running of the cars shall he stopped unless the leak is localised
and removed within twenty-four hours." A suitable switchboard
arrangement designed to fulfil these conditions of test is shown in
the diagram. The trolley wire is connected to the positive bus-bar.
The rail return is connected to the negative bus-bar.
Si is a single pole switch.
Sj, So S, are two-way switches.
A, is a recording ammeter, wound with two coils, one set reading
firom about one-tenth to three or four amperes ; the other reading
from one to ten amperes.
Ai is another recording ammeter, reading from one to twenty-five
amperes.
F. is a recording voltmeter, reading from two to twenty volts
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 131
P. is a sensitised paper pole tester.
Li a couple of Leclanche cells.
L. a battery of six Leclanchg cells.
E. and £■, are earth connections.
X. X. are wires going to the extreme ends of the rails.
I, 3, 3, 4 are connections for positive poles of four machines.
The main switchboard circuit breaker and other connections are
purposely not shown, as being unnecessary in this case.
rTolley h
To obtain the monthly record by testing the earth connections
{vide Regulation 5), the switch Si is closed, switch S^ is placed from
I to 3 and switch Sj is placed from i to 3, The circuit is thus com-
pleted from the two cells L., through Ai by one earth plate to the
other, the ammeter A^ recording the current.
To test the current returning by the earth connections to the
dynamo, which must be taken daily (or the connections must be as
indicated alt the time the plant is at work) {vide Regulation 6) ; close
switch Si, place switch S, from i to 2, also Sg from i to 2, then A,
will record the current returning by the earth connections. To test
or record the potential between the earthed return at the station and
)vGoO'^lc
i3a DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
the extreme ends of the earthed rail return (vide Regulation 7), one
or both methods may he used, as follows :— A recording voltmeter
V. in series with a wire from the end of the rail at one terminus to
the rail at the generating station, thus obtaining a continuous record
of the potential difference or voltage ; in the other case a battery of
six Leclanche cells, L., in series with a polarity recorder, P., inserted
in the circuit of a wire from the generating station end of the rail to
the other extreme end of the rail. So long as the difference in volts
between these two points on the rail is less than the Board of Trade
limit, the cells send a current from the generating end to line end,
and the polarity recorder, P., records it.
In the testing of the leakage current from the insulated portions of
the line (vide Regulation 10) it has to be done when the cars are not
running, either before commencing to run in the morning, or after
finishing at night. The car trolley arm and wheels are entirely dis-
connected from the trolley line, and the lines are fully chained.
Each machine is connected in turn to the line through the recording
ammeter A, and switch S,. This test has to be taken daily.
3. — Testing Electric Tramw^ay Circuits.
The Board of Trade set forth very stringent conditions regarding
the periodic testing of the electric circuit of a tramway installation.
The wisdom of such regulations is easily jierceived, for a proper
regulation tends to prevent injurious electrolytic action on gas and
water pipes, or other metallic pipes, structures, or substances. It
also minimises, so far as is practicable, interference with the electric
wires, lines, and apparatus owned by telephone, telegraph, and other
companies. These regulations, which are primarily formulated for
the protection of outside parties, are of great advantage to the tram-
way undertakings themselves, since, by systematic periodic testing,
excessive leakages of current are indicated, localised, and removed,
thus preventing the development of serious faults and undue waste
of energy. The results of the tests have to be permanently recorded,
and must be open for inspection at any time.
There are also quarterly and monthly tests, which deal with the
localisation and removal of leakages and time occupied, particulars
of any abnormal occurrence affecting the electric working of the
tramways, conductance tests, insulation resistance of insulated cables,
conditions of earth connections, etc. The " daily records " are :
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 133
(a) Number of cars running ; (6) number of miles of single tram-
way line; (c) maximum working current; (i) maximum working
pressure ; (e) maximum current from the earth plate or water
pipe connections; (/) leakage current; (g) fall of potential in the
return circuit.
Confining our attention to the " daily records," which are the most
important, we find, with regard to the fall of the potential in the
return circuit, that " when the return is partly or entirely insulated,
a continuous record shall be kept by the company of the difference
of potential during the working of the tramway, between the points
on the uninsulated return ; and if at any time such difference of
potential between any two points exceed the limit of seven volts,
the company shall take immediate steps to reduce it below that
limit."
When the return circuit is partly or entirely uninsulated, "the
current passing from the earth connections through the current
indicator to the generator, or through the resistance to the insulated
return, shall not at any time exceed either two amperes per mile of
single tramway line or 5 per cent, of the total current output of the
station. The insulation of the line, and of the return when insulated,
and of all feeders and other conductors, shall l>e so maintained that
the ' leakage current ' shall not exceed one-hundredth of an ampere
per mile of tramway. The leakage current shall be ascertained daily
before or after the hours of running of the cars, when the line is fully
charged. If at any time it shall be found that the leakage current
exceeds one-half of an ampere per mile of tramway, the leak shall be
localised and removed within twenty-four hours."
A difierent regulation applies when the line or return, or both, are
laid in a conduit ; this reads : " The leakage current shall be
ascertained daily, before or after the hours of running, when the
line is fully charged ; and if at any time it shall be found to exceed
one ampere per mile of tramway, the leak shall be localised and
removed as soon as possible. The maximum voltage allowed on
electric tramways is 550 volts."
For the purpose of ascertaining the value of these daily tests,
special recording and other indicators have to be installed in a
suitable place in the generating station. These instruments and
switches are generally mounted together in a convenient manner on
a slate or marble panel called a " Board of Trade test panel."
)vGoo'^lc
134 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
In the majority of cases the " Electric Lighting " and " Traction "
generating plans are installed in one and the same central station ;
BOABP OF TFADE PANtL
and in many cases the same generator can be used tor generating and
supplying energy either for electric lighting or tramway traction pur.
poses. The accompanying outline diagram illustrates a combined
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 135
" Lighting and Traction " arrangement as regards the electrical circuit
at the generatiDg station.
The multipolar generator can be used either for supplying current
for electric lighting purposes at a pressure of 460 volts, or for traction
purposes at 550 volts. This is easily controlled by changing over from
the lighting to traction side, or vice versd, by means of a change-
over switch, COS. The outlines of three panels are shown, the one
on the left being the "generator" panel, which contains the regulat-
ing resistance for the purpose of varying the voltage of the generator,
lighting and traction contacts, switches, circuit breakers, bus-bars,
meters, etc. The middle panel is the " traction feeder " panel, and
the panel on the right hand is the " Board of Trade " test panel,
which shows the circuit arrangement with the instruments and con-
nections, which go to the feeder switches for the tramway ; also the
pilot wire connections, which are connected to the faj end of the rails
on the different tramway routes.
The trolley line circuit is connected to the positive bus-bar, which
is in turn connected to the positive side of the generator. The rail
(earth) return circuit is connected to the negative bus-bar, which is
connected to the " negative " side of the generator.
The lighting circuit does not concern us, so we shall confine our
attention to the traction circuit only.
In the diagram: A = ammeter; K= voltmeter; F = fuse;
S.R. = shunt resistance ; W.Af. = wattmeter ; A .CO. = automatic
cut-out ; CB. = circuit breaker ; R.R. = shunt regulating rheostat ;
C.O.S. = change-over switch ; Com. = commutator ; and + B =
positive brushes ; — B = negative brushes; L.A. = lightning arrester ;
L.S. = lighting side; T.R. = traction side; ff. F. = recording volt-
meter ; Sh. = shunts for meters ; 5. = switches.
In the multipolar generator panel, the two bus-bars shown at the
top are the positive and negative traction bars. The voltmeter {Vm.)
indicates the " voltage " of the generator ; and the ammeter indicates
the current in amperes given out by the generator, when it is supply-
ing current for the traction circuits. There are two circuit breakers,
one connected to the positive and the other to the negative sides of
the dynamo. Below the circuit breakers is the main switch, which,
when placed in contact at the bottom, switches the generator on to
the traction bus-bars.
)vGoo'^lc
136 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
The shunt-regulatii^ resistance varies the voltage or pressure of
the generator.
In the traction feeder panel the positive and negative traction bus-
bars are shown at the top. From these are taken separate feeders
(only two are here shown). The number of feeders depends upon
the number of traction circuits to be supplied with current. All the
feeders are connected to the positive traction bus-bar; and each
feeder supplies current to a separate route. In each feeder circuit
is inserted a circuit breaker, which trips off (breaks the circuit) when
an excessive load comes on the feeder, or in the case of a wire falling
down or coming Into contact so as to cause a short circuit, etc. The
action of the circuit breaker is automatic, and renders the feeder dead
(out of circuit) for the time being.
There are also the ammeters, as shown, which indicate the amount
of current the cars are taking on that particular feeder or section.
Below the circuit breakers are the feeder switches, from which a
lead is taken to the wattmeter, which registers the power used on
that feeder circuit. The " shunt resistance " for the wattmeter is
connected to the negative bus-bar. A lead is taken from the
wattmeter to the hghtniog arrester, from which the feeder cable
is taken.
In the Board of Trade traction panel, the recording volt-
meter on the left-hand side records the voltage or potential
difference between the earthed return at the generating station
and the extreme far end of the earthed rail return. The
left-hand connection on the recording voltmeter is connected to
earth.
For the purposes of testing and obtaining a daily record of the
drop of voltage on the different routes, the pilot wire switch is placed
in contact with the several stud contacts, to each of which is con-
nected a pilot wire ; these pilot wires are run in the feeder ducts or
conduits, and are connected to the extreme far ends of the rails
on each separate route. They are generally bonded on to the
rail. A new recording sheet is fitted in the voltmeter each day ;
and a record is kept for reference according to Board of Trade
requirements.
The recording voltmeter on the right records the generator
voltage — !.«., the voltage between the positive and negative
traction bus-bais. The ammeter shown at the top of the panel
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE.
137
is for the purpose of indicating the amount of leakage current on
the insulated line for each route. This ammeter has two sets of
coils, one set reading from o'oi to 2 amperes, the other reading from
I to 10 amperes. This leakage current test has to be made when
-Three-phase Alternating Curreat Switchboard Circuit.
all the cars have stopped running and the trolley heads are taken
off the trolley line, after the cars have finished running at night.
The method of making the test is to leave the generator running,
but the circuit breaker is tripped, and all the feeder switches are out
of circuit. The switch between the recording voltmeter is then
)vGoo'^lc
ijB DYNAMO. MOTOR AND SWITCHBOARD CIBCUITS.
switched into circuit with whichever contact stud the running
generator is connected to ; then by closing the small tiimler switch
(shown at the right-hand side below the ammeter) the circuit which
contains the ammeter is completed, and a reading is obtained from
it whii h corresponds to the feeder or circuit to which the switch at
the bottom of the panel (tramway feeder switch) happens to be
connected.
It will be noticed that by placing the switch (shown on the feeder
connections at the bottom left-hand of the panel) in connection with
the several contact studs, that a connection is made from each separate
feeder through the leakage ammeter to the positive traction bus-bar.
The accompanying illustration (Fig. 122) shows the circuit con-
nections of a 5cx)-volt 350-kilowatt generator used for colliery lighting
and power supply for three-phase motors, A " three-phase motor,"
with " starter," is shown connected to the three-phase supply mains.
The direct current exciter, coupled to the generator shaft, supplies
current for the generator field, and also for continuous current
lighting.
4. — Diagram of Three-Phase Synchronising Gear,
Fig. 123 illustrates the switchboard connections appertaining to
the above title ; in which A = ammeters, F = fuses, S = switches,
and C.R. =^ cable receivers. The synchronising lamps and volt-
meters are shown, also the outlines of two three-phase generators
and feeders Nos. i and 2.
The general method of practically synchronising alternators has
already been explained ; also it is understood as previously described
under heading of " Paralleling " two- and three-phase generators that
after once having been " paralleled " it is then only necessary to
synchronise one phase. As seen from the diagram, the method
consists in synchronising by the combination of "voltmeter" and
"lamps." The "lamps" visibly show in a most convenient
manner the indication of the synchroniser; but the "voltmeter"
is a better and more reliable indicator than the "lamps," showing
the correct moment for closing the " paralleling " switch, for
the reason that it is more sensitive, thereby responding to
minute variations of pressure more readily. The "dead beat"
voltmeter is used in practice, it indicating instantly any slight
variation in pressure. In practice it may be considered that, firstly.
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 139
the " lamp " shows when the synchronism stage is being approached,
and finally the "voltmeter" indicates the exact instant when
synchronism occurs. On reading the accompanying drawing it will be
noticed (on the extreme left-hand) over switches S, and S, of Generator
No, I, that there are two pairs of contacts : the one located at the
right of each pair of contacts being connected to the synchronising
mts"
^.-3?? j/ V V V V V
I1I1I1M n
1
Fig. 123.- Diagram of Three-phase Synchronising Gear.
apparatus ; and those on the left are the main bus-bar connecting cable
contacts.
When a " generator " is to be switched in circuit, or " paralleled "
on to the " bus- bars," the switches S, and S^ are first placed on to
the "synchronising" contacts, and so soon as the moment of
" synchronism " is indicated by the lamps brightly glowing (without
flickering), and the voltmeter reads steadily, the switch is pushed
)vGoo'^lc
I40 DYNAMO. MOTOR AND SWITCHBOARD CIRCUITS.
forward, thus making contact with the main circuit contacts, at the
same time breaking the synchronising contacts and circuit. This is
a very convenient and practical method of making the main contact
at the same instant that the synchronising contact is broken.
5. Single-Phase Alternator with Exciter.
In the Fig. 136 Alt = single-phase alternator with slip-rings;
F.R. = alternator field resistance regulator ; F.S. is a double pole
\&y'^.
Fig. 114.— Single-phaae Allernalor wilh Exciter.
alternator field switch ; F.A. = field circuit ammeter ; P.V. = pli^
voltmeter inserted across the armature leads ; Ex — exciter (direct
current dynamo) ; Ex. F.R. = adjustable exciter field coil resistance ;
E.V, = exciter voltmeter ; A. = ammeter in main circuit which
indicates virtual amperes; H.T, Plugs = high tension plug switches ;
H.T. Fuse = high tension fuses in circuit with the feeders.
The method of starting, stopping, and running the exciter and
alternator in combination will be readily understood from the detailed
)vGoo'^lc
„Gooi^lc
i
I n.
'lutp. 141.
Gooi^lc
DIRECT, ALTERNATING AND POLYPHASE. 141
description of the practical method of working, under the heading of
" 2,000-Volt Alternating Current Plant."
Briefly, the mode of procedure is as follows : — Exciter armature is
driven up to normal speed, and its voltage is adjusted by means of
the regulating resistance (Ex. F.R.).
The alternator is speeded up ; the main field switch (F.S.) is
closed; and the current flowing through Che field magnet coils is
adjusted by the field regulator (F.R.). The alternator is inserted
into the main distributing circuit by means of the plug switches
{H.T. Plugs).
6. High Tension Single Phase Alternating Current Switch-
board (2,000 Volts).
With the object in view of making the description as simple, clear,
and easily understood as possible, the two illustrations (F*gi, i35and
126) should be read in conjunction with each other.
Fig. 125 is a facsimileof the complete switchboard, whilst Fig. 126
is a simplified diagram of Fig. 125.
It will be noticed in Fig. 125 that there are three machine panels,
viz., panels 3, 4, and 5. Each panel is incomplete taken singly, but
collectively they are complete ; the connections which are left out in
any of them are completed in the others.
The diagram of the essential and complete connections are shown
in machine panel (No. 2) of Fig. 126.
The enlarged and complete illustration of the "synchronising
panel" (No. 2) {Fig. 125) and panel 3 {Fig. ia6) is shown on the
extreme left-hand of Fig. 125.
This particular central station plant have six alternators, which
are represented by six plug holes on the synchronising panel (marked
I to 6) {Fig. 125).
The two bottom holes are merely " dummies," and are only for
the purpose of supporting the synchronising plugs, when not in use,
so that they will not loosely hang about.
It will be noticed there are two " synchronising plugs," one out,
showing its connections, and the other in position in the dummy.
The index to the figures is as follows : — V. ~ voltmeters; A, =
ammeters; Ex.A. = exciting ampere meter; K.W. or W.M. =
)vGoO'^lc
143 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
wattmeter, C.P. = circuit plug switches, A.P.P. = alternating
paralleling plug ; S.L. = synchronising lamp ; S.V. = synchronising
voltmeter ; Ex.S. = exciter switch ; F.S. = field switches ; F.R.
= field resistance ; F. = fuses ; B.S. = battery switch ; S.S. = ^
FiQ. 136. — Allematiog Carrent Switchboard.
Starting switch ; S.R. = starting resistance ; C.O.S. s= chaDge-
over switch ; R.C. = regulating cells ; B.R.S. = battery regulating
switch ; C. and D,M. = charge and discharge meter (aron meter).
In Fig. 125 No. I is the circuit panel; No. 2 = synchronising
panel ; Nos. 3, 4, and 5 are three of the alternating machine panels.
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 143
There are six of these, but as they are repetitions one of the other
three only are shown. In reality it is necessary to show only one.
No. 6 is the booster panel, and 7 the battery panel.
In Fig'. 126 Nos. I, 2, 3, 4, 5 and 6 represent respectively the
circuit, one machine, synchronising, exciter, battery and booster
panels.
The three secondary voltmeters on panels 3, 4 and 5 of Fig. 125,
to which no connections are shown, are connected to the secondaries
of the different transformers.
In Fig. 126, panel No. 4, it will be seen that this machine panel
has been altered to convert it into an exciter panel with the object
of not adding another panel to the existing switchboard ; the machine
field switch and rheostat are coupled up to the exciter as an " exciter
switch" and " exciter field resistance,"
It will also be noticed that the alternator connected to panel 5
drives its own exciter, it being used exclusively for itself, thus
panels 4 and 5 are used in conjunction.
In panel 4 {Fig. 12$) the exciter is shown as being coupled direct
to the field switch, instead of to the exciter bus-bars, and then from
the exciter switch to the field switch. This was so drawn with the
object of not drawing another exciter.
This is, however, correctly and clearly shown in exciter panel 4
of Fig, 126.
Referring to the figures, the operation of manipulating the board
and plant in practice is as follows : Assuming the alternating plant
is completely shut down, to start up first of all the exciter is started,
then the alternator. As the alternator is being gradually speeded
up, the exciter switch is closed, which puts the exciter in circuit
with the exciter bus-bars. Next the main machine switch is closed,
thus placing it in circuit with the alternator bus-bars, and finally,
closing the feeder circuit switches, a current is supplied to the
external circuit or feeder mains.
To bring the alternator up to the required voltage or E.M.F.,
first of all the exciter voltage must be correctly adjusted by regu-
lating by means of its field resistance F.R. After this the voltage
of the alternator is adjusted by altering its field resistance as the load
varies. In this particular case the normal value of the exciter
voltage is 120, but as the load 00 the alternator varies, the exciter
)vGoO'^lc.
144 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
voltage i<i altered, increasing as the load increases, until it
sometimes reads as high as 130 volts. The voltage of the alternator
is 2000.
If the load becomes too great for one machine, the next operation
is to put another alternator in circuit, i.e., in " parallel " with the one
already running.
The method of doing this is (assuming that one exciter is large
enough to excite the field -magnets of two alternators) to bring up
the exciter volts, then close the second incoming alternators field
switch, and, by regulating its field resistance, adjust the voltage
until it is equal to that of alternator No. i, already supplying current,
to bus-bars. Having got the field strengths of both alternators
approximately equal and voltage readings the same, now insert the
synchronising plug switches into their respective receptacles (see
synchronising panel at left-hand of Fig, 1 25), i,e., one into plug hole
connected to alternator i, and the other into plug hole alternator
Na 2, thereby placing one alternator acting by induction through
the intermediary of a transformer connected in series with the
incoming alternator, they being connected with a voltmeter and
glow lamp arranged in parallel.
When the two alternators are " in phase " the synchronising
lamp burns brightly (no flickering is seen), and the synchronising
voltmeter indicates the right voltage or E.M.F. (in this case 105).
When " in phase " the second alternator is inserted in " parallel "
with alternator No, i (already running) by instantly closing the rnain
alternator switch.
In this alternating current plant a separate transformer for each
alternator is used.
When one exciter was not sufficiently large to excite both alter-
nator fields, an additional exciter had to be " paralleled " on to the
exciter bus-bars. This is done by starting and speeding up the
second exciter until its voltage (regulated by means of its field
resistance) is equal to the E.M.F. of the exciter bus-bars, then
instantly closing the exciter mfun switch ; thus the bus-bars are now
supplied with current from two exciters in " parallel."
The load may be equally distributed between both exciters by
altering their field resistances to suit the varying loads or current
demanded by the field magnets of the alternators. Any additional
)vGoo'^lc
biRECT, AttERNATlNG AND POLYPHASE. I45
alternatoi may be " paralleled " on to the main bus-bars as before
explained.
Of course it is undeistood that the " exciters " are small direct-
current dynamos, and are used solely for the purpose of supplying
a direct current to excite the field magnetism of the large alternators.
The supply current is supplied and completed along the following
circuit:— from bottom bus-bar (panel i in both figures) to feeder plug
switch, through the switch to fuse, from fuse to external circuit,
and returning through fuse, ammeter, wattmeter, back again to other
side of switch, on to other bus-bar.
The battery (panel 5, Fig. 126, and panel 7, Fig. 125) is used for
exciting, and can be run in " parallel " with exciters already running
on the exciter bus-bars ; or it alone can supply current to the bus-
bars when the exciters are stopped. Thus the alternators field
magnets can be supplied by a direct current either (i) by the storage
battery, (3) by exciter or exciters in parallel, (3) by exciters and
battery in parallel combination. The battery really forms an
auxiliary supply, being used in case of big demand to assist the
exciters, or by itself in cases of small demand, so that the rotating
exciting machines may be entirely stopped.
The " booster " (panels 6, Figs. 125 and 126) is used for charging
the battery. The " booster " may either be driven by a separate
engine or else (as in this case) driven by a current taken from the
exciter bus-bars, and it can only be driven (thus charging the
battery) when there are no alternators being supplied from the bus-
bar, for the reason that the exciter voltage has to be varied so as to
drive the booster motor at varying speeds, to produce varying
voltages in the generator or dynamo half of booster, which is neces-
sary at various stages of the battery charge ; therefore the " battery "
is charged by means of the " booster," driven by a current taken
from the exciter bus-bars, which buses are supplied with a current
of suitable voltage generated by a mechanically- driven exciter (».«.,
a direct current dynamo).
The method of charging is as follows ; Assuming the storage
battery to be in a discharged state, and the "change-over-switch"
and " paralleling switch " are thrown over out of circuit ; first, all
the regulating cells are placed in circuit ; secondly, the exciter is
speeded up and the voltage regulated (by means of its field resistance)
)vGoo'^lc
146 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
and then switched on to the exciter bus-bars, thus supplying them
with current.
Next the booster starting switch (S.S. Fig. 126) (this is on the
motor armature side that takes current from the exciter bus-bars,
and is electrically driven, which mechanically drives the generator,
booster, or dynamo armature side, generating in it a current of suit-
able voltage which charges the battery) is closed, and gradually
cutting out the starting or regulating resistance (S. R. Fig. 126) (this
is also in the motor half of the armature) the speed of the armature
increases, which increases the voltage and current of the dyn^no or
booster half of armature, and in addition the speed of the motor
booster is increased or diminished by varying the speed of the exciter
and r^ulating the exciter field resistance, thus varying the exciter
bus-bar current and voltage as desired.
The " booster " voltage is thus regulated so as to equal the
" battery " voltage, and the E.M.F. must be equal in each case
before " paralleling."
Assuming we have attained this latter condition, the "battery"
throw-over switch is now forced to the bottom (charging) contacts
(panels 7 Fig. 125 and 5 Fig'. 126), and finally "parallel" the booster
and battery by closing the " paralleling switch " B.SJ^.S. (panel 5
Fig. 126).
A charge is now given to the " battery " by increasing the voltage
of the " booster," causing it to force a charging current of appro-
priate strength through the storage battery until fully charged. The
volt^e of the booster will have to be raised considerably towards
the end of charge, for the battery voltage at this sti^e rapidly rises.
The amperes, or normal rate of charge, required for the battery in
this particular case is 40 ; the length of time to fully charge varies,
of course, with the extent of previous discharge.
The "charge" and "discharge" current is indicated by the Aron
meter (panel 5 Fig'. 126).
When the battery is fully charged, the "booster" has to be
switched out of circuit, in which the operation is the reverse of
switching in circuit, i.e., gradually reduce the booster voltage, thus
diminishing the load, until there is neither " charge " or " discharge "
(no flow of current) taking place between " booster" and " battery";
then quickly puU off the " paralleling " switch, and immediately
)vGoO'^lc
DIRECT, ALTERNATING AND POLYPHASE. 147
afterwards take the change-over switch off the bottom (charge)
contacts.
The "booster" may be switched out of circuit with the exciter
bus-bars by means of the regulating resistance and opening the
switch S.S., after which the exciter may be slowed down and
switched out of the circuit.
To " parallel " the charged battery with the exciter on to bus-bars,
first regulate the battery voltage equal (by means of battery regu-
lating cells) to the exciter voltage (in this instance lao to 130 volts),
then push the battery change-over switch on to top (discharge)
contacts, and quickly close the "paralleling" switch ; then, to give
the battery a load (or cause it to discharge to assist exciters), switch
more cells in circuit ; then insert more resistance in the exciter fields,
thus taking part of the load from off the exciter, and distributing it ;
giving some to the battery.
In this particular plant some of the alternators had their own
exciters (i^,, they were not supplied from the exciter bus-bars),
therefore the battery charging by means of the booster driven from
the exciter bus-bars did not affect the alternators, and they could
remain running while the battery was being charged.
7. Combined Lighting and Traction Direct Current
Switchboard Arrangement.
In the accompanying diagram, Fig. i2y,A. = ammeter ; F. = fuses ;
S.R. = shunt resistance ; S. = switches ; £ ■ = lamp ; B.H.L . = boiler
house hghting ; B.H.M. — boiler house motors ; E.H.M. = engine
house motors; P.M. = pump motors; W.L. = works lights;
E.B. = enrth bar; K. = voltmeter ; P.S. = paralleling switch;
Boos.V. = booster voltmeter; Bati.V. = battery voltmeter; A.M. =
aron meter; W.M = wattmeter; R.V. = recording voltmeter;
A.C.O. = automatic cut out; M.S.R. = motor starting resistance;
M.H'.^middle wire bar; Reg, C«i/s = regulating cells; C.B.=
circuit breakers; fl.i?. = shunt regulating rheostats; CCS. = change-
overswitch; C.O.M. =^ commutator; -|-B. = positive brush; -B.=
negative brushes ; Z,.^. = lightning arrester; F.ff, = fixed resistance
in series with the generator ; E.G. = electric governor ; L.S. = light-
ning side ; T.S. = traction side. By means of COS. it is possible to
switch over the generator on to the lighting or traction side. The
voltage for lighting is 460, and for electric traction is 550. The top
)vGoo'^lc
148 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
seven panels are " bus-bar " panels, the lowei eight panels are
the switchboards for (i) works, (2) balancer, {3) battery booster,
(+) battery, (5) multipolar generator, (6) traction feeders, {7) steam
turbine generator, and (8) the Board of Trade testing panel for the
electric tramways.
The seven top bus-barpanelsareforthelightingand motor circuits,
and the voltage between the positive and negative bars is 460.
Referring to the " works" panel (No. i), the ammeter on the left
shows the amount of current taken between the positive and middle
wire by the works, and the ammeter on the right shows the amount
of current taken between the negative and middle wire. The top
row of switches are for the lights in the switchboard room, the
middle row of switches are for the boiler house lights, boiler house
motors, engine house motors, and pump room motors connected on
the positive side ; and the bottom row of switches are connected to
the engine room and boiler house lights and motors and pump house
motors on the n^ative side.
In the " balancer " panel (No. 2), the ammeter on the left shows
the amount out of balance on the "negative" side, and the right-
hand ammeter the amount out of balance on the positive side. The
two voltmeters indicate the voltage on the positive and negative
sides of the middle wire. The resistance below the voltmeters is
the starter for the balancer. The two outside switches below the
resistance supply current from the " bus-bars," the left-hand switch
from the negative bus-bar, and the one on the right from the positive
bus-bar. The middle switch is the middle wire switch.
In the "battery booster," panel (No. 3), the voltmeter on the left
indicates the voltage of the " booster " and the right-hand voltmeter
the " battery " voltage. These two voltages must be equal before
the " paralleling switch " is closed, in order to parallel the " booster "
and " battery " to charge. The " aron " meter below registers the
amount of " charge " or " discharge " of the " battery " ; below this
is an " automatic cut-out." This is placed in " series " with the
meter and will cut or " blow out " in the case of short circuits, great
overloads, etc. ; thus cutting the " battery " out of circuit whilst
being charged or discharged. The two small switches below the
A. CO., are always left closed, and could be done away with by
jointing the cables direct instead of connecting to the switches. The
two larger switches (one on each side of these smaller ones) supply
)vGoo'^lc
Gooi^lc
jv-Goex^lc
DIRECT, ALTERNATING AND POLYPHASE. 149
current to the " booster," the left-hand switch being connected to
the " positive " bus-bar, and the one on the right to the " negative "
bus- bar.
The switch (P. S.) on the extreme left is for " paralleling " the
** booster " and " battery." The " resistance " below the switches
is the " starter " for the " booster," the two " leads " as shown
going to the centre of the switch. The fuse (F.) below is to prevent
any excess of current going through the armature, as in the case of
starting with all " resistance " out of circuit.
In the " battery " panel (No. 4) the four meters on the top are
two voltmeters and two ammeters, the voltmeter on the left indi-
cating the voltage on the " positive " side, and the one on the right
the voltage on the " negative " side of the battery. The " ammeter "
on the left is a "centre reading" one, ».«., when at "zero" the
needle is in the centre ; when the needle is pointing to the " left-
hand " side of zero it indicates that there is a charge going into the
battery, and the volume of the charge ; when pointing to the right
of zero it indicates that there is a "discharge" on the "positive"
side of battery. The "ammeter" on the right is an ordinary one,
which necessitates having a plug arrangement to show if there is a
"charge" or "discharge" on the "negative" side of the battery.
The " plug " connections are shown on the right-hand side of the
" change-over switch." Below the meters is the " change-over '*
switch for the battery, which, when switched on to the " top "
contacts, connects the " battery " circuit to the " lighting " bus-bars,
and when switched on to the " bottom " contacts, connects the
" battery " to the " booster " ready for being " charged,"
Below this are the contacts for the " regulating cells." There
are four undivided bars, which act as guides and conductors for their
respective sliding contacts, there being two each for the " positive "
and " negative " side of the "battery." There are two "sliding"
contacts, one each for the "positive" and "negative" sides, and
they connect the smalt " divided " bars with the long continuous bar.
Two cells of the "battery" are connected to each of these divided
bars. When the sliding contacts are at the top of the small bars all
the " regulating " cells are in circuit ; and when on the bottom bars
all the " regulating " cells are out of circuit.
In the " multipolar generator " panel (No. 5) the two " bus-bars "
shown at the top are the " positive " and " negative " traction
)vGoo'^lc
ISO DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
bus-bars. The " voltmeter " indicates the " voltage " of the machine,
and the ammeter the load on the machine, when it is supplying
current either for " lighting " or " traction." There are two machine
" circuit -breakers," one connected to the " positive " and the other
to the " negative " sides of the dynamo. Below (he " circuit-
breakers," is the "main switch," which when placed in contact
at the top switches the " generator " on to the " lighting " bus-
bars; and when placed in contact at the bottom switches the
generator on to the " traction " bus-bars. The " shunt " regulating
resistance varies the " voltage" of the generator.
In the "traction feeder" panel (No. 6), the "positive" and
" negative " traction bus-bars are at the top. From these bus-bars
are shown two separate "feeders"; the number of "feeders"
depends upon the number of "traction" circuits to be fed with
current. All the " feeders " are connected to the " positive " traction
bus-bar, and each " feeder " supplies current to a separate route. In
each "feeder" circuit is inserted a " circuit -breaker," which trips
off when an excessive load comes on the feeder (such as a fallen
wire, causing short circuits, etc.), thus making the feeder dead.
There are also the " ammeters " as shown, which indicate the
amount of current the cars are taking on that particular feeder
or section.
Below the "circuit-breakers" are the "feeder switches" from
which a " lead " is taken to the " wattmeter " which registers the
amount of current used on that feeder circuit. The " shunt resist-
ance " for the " wattmeter " is connected on to the " negative " bus-
bar. A lead is taken from the " wattmeter " to the " lightning
arrester '* from which the " feeder cable " is taken.
In the " generator " panel (No. 7) this is similar to panel Na 5,
only a " Parsons " steam " turbine " generator is shown instead of
the E.C.C. " multipolar " generator.
In the " Board of Trade " traction panel (No. 8) the *' recording
voltmeter " on the left-hand side records the " voltage " or potential
diflfereoce between the " earthed return " at the generating station
and the extreme ends of the " earthed " rail return. The left-band
connection on the " recording voltmeter " is connected to earth.
For the purposes of " testing " and obtaining a " record " of the
" drop " on the different routes each day, the " pilot " wire switch is
placed in contact with the several stud contacts, to each of which is
)vGoo'^lc
DIRECT, ALTERNATING AND POLYPHASE. 151
connected a " pilot " wire ; these are run in the feeder ducts or con-
duits, and are connected to the extreme ends of the rails on each
separate route. They are " bonded " on to the rail. A new
"recording sheet" b fitted in the "recording voltmeter" each
day, and 3 " record " kept for reference, according to " Board of
Trade " regulations.
The " recording voltmeter " shown on the right records the
" generator " voltage, it., the " voltage " between the " positive " and
" negative " traction bus-bars.
The "ammeter" shown at the top of the panel is to indicate the
amount of "leakage" on the "insulated" line for each route.
This " ammeter " has two coils, one set reading from -oi to 2
amperes, the other set reading from i to 10 amperes. This " leak-
age " current test has to be taken when all the cars have stopped
running and the trolley heads taken off the line, and the " test " is
taken after the cars have finished running at night. The method of
taking the "test" is to leave the "generator" running, but the
" circuit-breaker " is " tripped," and all the " feeder switches " are
out of circuit. The switch between the recording voltmeters is then
switched into contact with whichever contact plug the " running
generator "is connected to, then by closing the small " tumbler "
switch (shown at the right-hand side below the ammeter) the
circuit which contains the ammeter is completed, and a " reading "
is obtained from the ammeter, on whatever feeder or circuit the
switch at the bottom of the panel happens to be connected. It will
be noticed that by placing the switch (shown on the feeder connec-
tions at the left hand of panel) on to the several contact studs,
a connection is made from each separate " feeder " through the
leakage ammeter to the " positive " traction bus-bar. Each
" generator " is connected in turn to the line through the indicating
ammeter and switch S\ F is a fuse placed in the ammeter circuit
so as to protect it,
In connection with " three-wire " systems of distribution, in order
to take the out- of- balance current in the " neutral " wire, when the
two sides are unetiually loaded, either two batteries, or a pair of
machines mechanically and electrically coupled together, are inserted
at any convenient place in the system. These latter are known as
" balancers," their object being to balance or equalise the voltage
and current on each side of the neutral.
)vGoo'^lc
152 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
When there is no current in the middle wire, the balancers will
run as motors in series with the two outers, m., the positive and
negative mains ; and since they are unloaded, the current will only
be that required to overcome the losses in the machines themselves,
as the speed will be very high.
The neutral wire, however, nearly always carries some current
for it is seldom that the demand for power is equally distributed
between the two sides.
Generally the voltage on the lightly loaded side tends to rise, and
on the heavily loaded side to drop by an equal amount, and this
brings the " balancers " into action, their function being to minimise
the " drop of pressure,"
The action is as follows : — Half the current in the neutral flows
through the machine on the lightly loaded side, causing it to run as
a motor, thereby driving the other machine as a dynamo, which will
supply an equal amount of current to the heavily loaded side.
In the compound-wound machines the drop of voltage can be
reduced to zero, or even be converted into an actual rise in voltage
on the more heavily loaded side by suitably proportioning the
" series " and " shunt " windings.
The windings of both machines are connected exactly as for com-
pound dynamos, so that so soon as one machine begins to run as a
motor, the "series" winding on it acts in opposition to the "shunt"
winding, and this reacts and tends to assist the compound winding
on the dynamo machine to raise the volts on the heavily loaded
In this way the combined action of the two " series " windings
can either be made to keep constant volts on the two sides of the
system, or to raise the volts on the more heavily loaded side, and so
compensate for " drop of pressure " in the neutral.
It is, for practical reasons, advisable to have a regulating resist-
ance in the "shunt" windings, to enable the voltages on the two
sides of the system to be controlled by hand when required.
Referring to Figs. 127 and 128, the field of the booster is " shunt "
wound, and provided with a shunt regulator, which allows a wide
variation of volt^e across the booster armature.
The shunt motor coupled mechanically to the generator or booster
is clearly shown j and the speed of the motor, and therefore voltage
)vGoO'^lc
DIRECr, ALTERNATING AND POLYPHASE. 153
)vGoo'^lc
IS4 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
of the booster, is controlled by means of the motor armature starting
resistance or regulator M. S. i?., and the field voltage of the " booster"
ilself is in addition regulated by the 6eld regulating resistance
{Fig. 128). The regulatins cells of the battery are connected to the
booster and bus-bars through the intermediary of a sliding contact
regulator, which places more or less number of "end cells" in
circuit as desired, and the change-over switch C. O. S. Figs. 1 27 and
128 either switches the booster in circuit with the battery, or cuts
out the booster and switches the battery directly on the bus-bars ;
and when in the " off" position, as shown in Figs. 127 and 128, the
" battery " is out of circuit with both the " booster " and the " bus-
bars."
To charge the battery the change-over switch C. 0. S, is switched
to the "off" position, and all the cells are placed in circuit by means
of the sliding contact regulator.
The motor is then started and run at full speed by closing the
stai ting switches and cutting out the armature starting resistances
M. S. R, This action speeds up the booster, and by regulating the
field resistance {Ftg. 128} the booster voltage is caused to equal the
battery voltage across the outers. This being done, the " booster "
is " paralleled " or inserted in circuit with the " battery " by pushing
over the change-over switch C. 0. S. on to the bottom contacts (».«„
charge side), the battery being fully charged by cutting out more and
more of the "field resistance" of the "booster."
The battery under consideration requires a normal charge of 200
amperes, the length of time to charge fully varying according to the
extent of previous discharge. The aron meter indicates the amount
of charge or discharge.
To switch the " booster" out of circuit the operation is reversed,
which consists in adjusting the booster field resistance and motor
starting regulator until the aronmeter indicates no flow of current,
and the battery circuit is quickly opened by the C. 0, S., after
which the motor booster may be cut out of circuit, slowed down
and stopped.
The operation of inserting the battery in circuit with the lighting
bus-bars is as follows : The battery voltage, as indicated by the
voltmeter, is brought equal to the voltage of the bus-bars or generator
feeding the buses by adjusting the sliding contact regulators over
the regulating cells of the positive and negative sides of the battery.
)vGoo'^lc
DIRECT. ALTERNATING AND POLYPHASE. 155
The voltages l>eing equal, the next thing is to put the plugs or
switches (Figs. 127, 128) in circuit with the + and - bus-bar battery
panel, and lastly, "parallel" the battery with the bus-bars by
pushing the throw-over switch in circuit with the top contacts ;
thus the battery and bus-bars are in circuit, and the booster cut
out.
A toad can either be given to or taken from the battery by means
of the regulating battery switches, i.t., a charging current can be
sent into the battery by reducing its voltage below that of the bus-
bars by adjusting the regulating cells by means of the sliding con>
tacts ; and the amount of current received by the battery will depend
upon the difference of potential between the terminal battery voltage
and bus-bar voltage, thus loading the generating dynamo, it now
having to supply current for both the bus-bar circuit and the
" storage battery " ; or a " discharge " from the battery to assist the
generator may be obtained by adjusting the sliding regulating con-
tact so as to place more battery cells in circuit, thereby raising its
E, M. F. or voltage sufficient to cause a discharge to supply the
bus- bars.
A battery under the above conditions will act as a " balancer,"
and in the particular case under description is so used,
During periods of light load on the bus-bars, the generating
machine can be cut out of circuit by switching off when its voltage
is just a very small percentage lower than the bus-bar battery
voltage, and then slowing down until stopped. The battery then
supplies the lighting current.
If the battery, during periods of heavy demand for current, has
been assisting the generator by working in " parallel " on the supply
bus-bars, thus becoming wholly or partially discharged, its voltage
would eventually drop so much that with all the ceils in series its
voltage could not equal the bus-bar voltage. It can be cut out of
circuit by first placing a machine " balancer " in circuit with the bus-
bars {Fig. 127, panel 2), after which the battery voltage is so regu-
lated that there is neither a charge or discharge current taking place
as indicated by the ammeter ; then quickly switch off by means of
change-over switch C. 0. S. The battery can afterwards be fully
charged by the booster as before. This battery is used to take the
lighting load at night time (during the hours of small demand), and
during the remainder of the time (day time), when not being charged,
)vGoo'^lc
156 DYNAMO, MOTOR AND SWITCHBOARD CIRCUITS.
is used for "balancing" (either alone or in combination with the
other machine balancers). It will be noticed (panel 4, Fig. 127, and
Fig. 128) that when the change-over switch is placed on the top
contacts, it inserts the " battery " in circuit with the lighting bus-
bars. To use it as a " balancer," the'voltage has to l>e regulated by
hand (it not being automatically regulated as in the case of a machine
balancer), and this is done by moving the battery regulating switches
across the terminals of the regulating cells, which thus cuts in or out
of circuit (thereby varying the voltage) one or more cells as occasion
demands.
When the " out of balance " current is becoming excessive (say 80
or 100 amperes more on one side of the system than the other)
another balancer (machine) is inserted in the bus-bar circuit, to
run in " parallel " with the one already running (either " battery
balancer " or machine balancer or both). This does not interfere
with the battery, which can be left connected to the bus-bars, and a
"charge "can flow into the battery from the " bus-bars " ; whilst
the "balancer" or "balancers" take care of any "out-o(-balance"
current that may occur.
Assuming that there is only the " battery " in " parallel " with the
bus-bars, and being used for " balancing," and that it now requires
" charging " before it can be taken off the bus-bars, another balancer
(machine) has to be inserted in the bus-bar lighting circuit for
balandng purposes.
To insert the balancers (panel 2, Fig. 127) : First close the two
outside switches S., and gradually cut out of circuit the "starting
resistance " ; when the balancer is rotating at its full speed close the
middle wire {E. B.) switch S, To take the " balancer " olF the " bus-
bars " reverse the operation, 1.*., break the middle wire switch S.,
then the two outside starting switches S. S., and insert the resistance
in circuit. When two balancers (machine) are running at the same
time in " parallel " on the bus-bars an equalising switch is closed
{Fig, 129) for the purpose of equalising the " out-of-balance " current
on both machines.
After the battery is fully charged by means of the booster as pre-
viously described, it can again be placed on the " lighting bus-bar "
circuit, when the machine balancer can, if desired, be taken off, thus
allowing the " battery " to do the balancing, or else leave the balancer
running, and either " discharge " the battery into the bus-bar circuit
)vGoO'^lc
i
DIRECT, ALTERNATING AND POLYPHASE.
157
(thus relieving the generator of some of the load), or allow a small
" charge " from the bus-bar to go into the battery. The act of either
sending a charge into the bus-bars (discharging the battery into the
bus-bars) from the battery, or, vice vend, sending a charge current
into the battery from the bus-bars, is brought about by regulating
the voltage of the battery by means of the regulating switches and
cells as previously described.
The " booster" is an ordinary shunt -wound machine driven by a
shunt-wound motor coupled direct on to the same shaft. It is not
reversible, and is used only for chaining the battery.
It will be noted in the arrangement so far described that to run the
Fig. 139.— Paralleling of Balancers.
booster for charging it necessitates the employment of a separate
generator, which does not prove economical.
In the arrangement as set forth in Ftg. 130 the " booster " can be
driven from the same generator that is supplying the " lighting load,"
and thus helps to load the generator.
This is accomplished by inserting a " regulating resistance " in the
booster generator field, thus enabling the attendant to raise or lower
the booster generator volt^e without altering the bus-bar or lighting
The accompanying illustration {Fig. 130) dii^rammatically shows
the booster and battery panels in which
V, •= Booster voltmeter.
Vi = Bus-bar voltmeter.
Vt = Booster generator voltmeter.
)vGoO'^lc
Diq.izeobvGoOi^lc
DIRECT, ALTERNATING AND POLYPHASE. 159
Vf = Voltmeter for indicating the voltage of the cells, coupled up
for charging, either on the positive or n^ative sides,
V, and Fj = Positive and negative voltmeter.
Ai and Af " Positive and negative ammeter.
A. — Booster ammeter,
R.R. = Field regulating resistance on generator side of booster,
S.R. " Armature resistance for motor side of booster,
C.O.S. = Booster change-over switch.
B.C^O.S. — Battery change-over switches.
S.S, = Booster charging switches.
F. = Fuses.
C.H.M. = Chamberl^n and Hookman meter.
R.C. = Regulating cells.
G. = Generator side of booster.
M. = Motor side of booster.
+ B£. and - B.S, = Booster bus-bars located in the battery room.
L.L. = Sliding leads for coupling to any number of cells it is desired
to charge.
Operation of Charging the Whole of the Battery by
means of the Booster.
(i) Switch a "balancer" into the "bus-bar" circuit as previously
explained.
{2) Cut out the "battery" from the "lighting" bus-bar circuit
by means of change-over switch B.C.O.S. {Fig. 130).
{3) Switch the "booster" into booster bus-bar circuit by means
of booster plugs (panel 3, Fig. 127).
(4) Start the booster by closing switches S.S. and cutting out
resistance SJ?. (Fig. 130).
(5) Change over the two booster change-over switches COS. on
to the bottom contacts, and then regulate the booster voltage (by
means of the booster generator field regulating resistance RM.,
which voltage is shown on voltmeter V.) so as to equal the battery
voltage (shown by V,).
(6) The "booster" is now "paralleled" with the battery by
throwing on to the bottom contacts the "battery change-over
switch" B.C.O.S. The value of the charging current flowing into
)vGoo'^lc
i6o DYNAMO, MOTOR AND SWITCHDOARD CIRCUITS.
the battery is indicated by the ammeter A., and is regulated by the
resistance R.R.
To " cut out " the " booster " from the " battery " the operations
are reversed.
Operation of utilising the Booster to charge only a few
cells on either the positive or negative side.
Proceed as in (i), (z), (3), explained atrove.
(a) Couple the leads LX. (located in the battery room) on to any
number of cells it is desired to charge (say ten).
(To bring down the voltage of the booster generator field to equal
the voltage of the number of cells it is desired to charge, considerable
resistance has to be inserted in its field.)
The leads L.L. can be moved any where along the booster bus-bars
B.B., these bus-bars being placed or conveniently suspended over
the cells.
(b) Start the booster by means of switches S.S. and resistance
S.R., then switch over one of the booster change-over switches
C.O.S. on to the top contact, and after the booster generator volts
(indicated by voltmeter V,) equal the voltage of the cells to be
charged (shown by voltmeter F,) the "booster" is then "paralleled"
with the " cells " by switching over the other change-over switch on
to the top contact. The booster generator voltf^e is regulated by
means of the resistance R.R., and the amount of charging current
Sowing into the cells is indicated by ammeter A.
The Chamberlain Hookmau meters are for registering the amount
of charge or discharge of the battery in units, so as to get the
" efficiency " of the battery.
The connections of battery volmeters and ammeters, V^ Vi, Ai, At
{Fig, 130), are shown on panel 4, Fig. 127.
)vGoo'^lc
INDEX.
ACCELERATE or lead, capacity, 7
Acceleration, 50
150
Accumulator cars, 68
variation of pressure, 70, 71
" Actual power," how obtained, 6
Advantages and disadvantages of stor-
age batteries for accumulator
cars, 68
of polypliase motors, 92
— ■■■ and disadvantages of " Mesh" and
"Star" methods, 92
Alternating current switchboard, 140,
141, 143
current switchboard connections,
ri6, n7
current " sub-station " counec-
current circuit, properties of, 5
Alternations or reversals, 2
, methods of finding, 2
Alternators, I
ia syndironism, 11
, mean value of E.M.F. and cur-
, single-phase in parallel, 107
, to parallel by means of syn-
chroniser, 87, 88
Ammeters, 77, 78, 79
, differential, 79
Amperes, virtual, 3
"Apparent power," how obtained, 5,6
Armature reactions, how compensated,
84
Asynchronous and synchronous, advan-
tages and disadvantages of, 10
Automatic brake cut out, 66, 67, 6S. 69
device for alternating generators.
Auto-starter, 36, 37, 38. 39
Auwliary phases, 96, 97, 98, 99
poles. 39-4»
n value of E.M.F. and
BALANCER and batteries on three-
wire system, 75
, object of, 75
Balancers, object of, 74, 75
, on three-wiro system, 73, 74
, regulation of pressure, 73, 74
Batteries and balancer on three-wire
system, 73
, object of, 73
and boosters on three- wire sjratem,
76,77
, storage, 73, 76, 77, 78, 79, 80, 81
Battery, charging and discharging,
r45, 146, 147, 155, 159
and booster, 71, 72, 148, 158
and booster circuit, 133, 158
operation, 154, 133, 159
Board of Trade regulation, izg, 130,
Booster and battery coimections, 71,
7i, 153. 158
1 battery and dyn
exciter, 84, 86
, object of, 71, 72
, reversible, 82, 83, S4, 83, 86
, Highfield, 82, 83, 84, 85, 86
, reversible field magnets lami-
nated. 84
, object of, 84
, use of battMy charging, g
, feeder, reversible, g
Boosters, 76, 7^, 79, 80, 81
and batteries on three- wire system,
76.77
)vGoo'^lc
Bl^lie, eddy curreot, 115, 116
, electric, 52, 53, 36, 57
, Importance of electric, 53
.method of connecting, 57
, object of electric, 53
, powerful, 51
Braking effect, powerful, 58
— — , connections to produce, j
Brush, controller wiring, 59
— , system of car wiring, 60
.system of "series-parallel" c
troUer, 39
Bus bare, 76
, auxiliary. 76
, charging, 76
— -, main, 76
bymeansoftransformersand
voltage, 111
Capacity and inductance, effects of, 7
, opposite effects of, 7
neutralise each other, 7
and self-induction, 96, 97
■ — , effects of, gb, 97
and condenser, 7
, influence of, 7
Car wiring, Brush, 60
Cell, end, 149
, regulating, 149
Cells, charging few by booster, 160
Charging few cells by booster, 160
Choking coil, 96, 98, 99
, object of, 96
, self-induction, 96
, discriminating, iiS, 119
, description of, 119
, object of, 119
coils, three-phase, 115
, adjustable, 115
(function of, 116
or impedance coil, effect of, 7
Circuits, auxiliary, 96, 97, 98,99
, primary and secondaiy, 7
Clodcwise and counter clockwise rota-
tion of armature in series and
Bhuot motor, 30, 31. 31, 33. 34
compound, 25
Commutating poles, 39, 41
Commuting field magnet colls, 4S
Compensatiog poles, 39, 42
Compensation of armature reactions,
84
Complete wiring connections, Brush, 63
Compound dynamo, clockwise and
counter clockwise rotation of
armature, 25
dynamos in parallel, iS, 19
, directions for starting
and slopping same,
iS, 19
motor, 34-40. 4J
, differential wound, 35
— — , object of, 35
, description of, 13, 14
— , object of, 13, 14
Condenser, 97
and capacity, 6
, capacity of, 97
, object of, 97
Constant speed motor, 26
differential wound, 35
Controller, action of, 50, 31
and wiring diagram of car con-
nections, 58, 59
diagrams, 64, 63
, Brush, 59
, contact pieces, 53
connections. Brush, 6t
development, 126, 127
of, 49, 67
, method of commuting the field
magnet coils, 48
, object of, 44, 46
, saving of power by using, " series-
parallel," 53
, spindle. 33
, '■ series-parallel," 48, 50, 51, 52,
33- 34
, for electric vehicles, 66
, stationary fingers, 33
wiring, Brush, 52. 62
Converters, rotary, 9
Copper, economy in weight in poly-
phase work, 103
Counter-E.M.F., 48—50
Ciirrents, polyphase, 89, 90, 91, 92, 93,
94. 93
Cut-out, a-jtomatic brake, 66. 67, 68, 69
Cut-outs, discriminating, 118
Cycle, I, X
Cylinder, object of reversing, 53
T^EFINITIONS of dyna
)vGoo'^lc
Dinerenlial wonad conipoDtid motor,
, object of, 35
Di-phase, 4
Directions for starling and slopping
dynamos in parallel, t6, 17, 18, 19
Discriminating cut-ODts, 118
choking coil, 118, iig
, description of, xrg
, object of, 119
Distribution bji single -phase,
tension three-wire system, 106
Dynamo, booster and battery con
35
63,14
, long-shunt, 14
, short-shunt compound, 14
1 shunt, 14
, alternating current, i
, continuous or direct cuireat, 1
, definition of, 1
, series, clockwise and counter-
clockwise rotation of armature,
23.24
, senes. wound, la
, shunt wound, 13
, compound wound, 13
, shuot wound, directions for
starting and
stopping, IS
, on constanl potential
incandescent lighting
circuit, 15
, to find positive pole, 21
, rotation of armature in shunt
machine, 21, 23
, clockwise rotation, 22
—— , counter-clockwise, 23
Dynamos, testing polarity of, 19
^ , lamp method, ig, 20
, voltmeter method, 20,
ECONOMY of polyphase
SLon, 92
Eddy current brake, iij
Effect lagging, gS
— -, leadinR, 97
Electric brake, 35, 56, 57
, importance of, 53
Electric brake, method of connecting.
-- — , three-phase transformers,
vehicle, eiplanation of controllers
for, 68, 6g
, " series-pw^lel " controller,
66,67
E.M.F., back or counter, 50, 35
End-cell switches, 70, 71, 75, 79
-, charge and discharge,
71. 14?
1 , object of, 70, 71
Equalisers, or balancers, 9
, object of, 73, 74
, on three-wire system, 73, 74
, regulation of pressure by, 73, 74
Exciter, booster, 84, 86
HAULT TEST PANEL, 127, 128—
Field magnet coils, method
muting, 48
— , short circuiting of, ag,
30
Field r^ulators, 38, 39
laminated in booster, 84
Formula, fundamental, for dynamo
design, 4
Frequency, 2, 3
Frequencies adopted in practice, 2, 3
, standard, 3
Fundameutal formula for dynamo
G EARLESS MOTORS, speed of,
68
Generator, three-phase, iii
Generators, paralleling of two-phase.
H
IGHFIELD BOOSTER, for
lighting work. 82, 83
-, for traction work, 84, 85, 86
)vGoo'^lc
Highfleld booster, object of, and how
attained, 83, 84, 85, 86
High-pressure feeders, iii
IMPEDE or retard, EelMndoctance,
Impedance, 7
or chokiiig coil, effect of, 7
loduciance ajid capacities, eflecl of, 7
— , opposite effects of, 7
■, neutralise, 7
regulator, 105, 106
Inductive drop in windings, 119
LAG and lead, 7
Lagging effect, 96
Laminated G eld-magnets in
booster, 84
, object of, 84
Laminated iron circuit, S
field in booster, 84
Lamp method, testing polarity of
IS, 19, 2
Lamps, synchronising, 107, 108
— — , pilot, 107, 108
, test, green and red, 117, 118
Lead and lag, 8
or accelerate, capacity, 5
, peroxide of, 21
Leading effect, 97
Lighting and power by low-tension
three-phase system, 106
Low-tension, three-phase system, loG
, distribution by single-phase
three-wire system, 106
Motor-drcuit, sparkless breaking of, 29
, clockwise and con nter-clock wise
rotation of armature in series,
30, 3t
, compound, 34
■ . shunt, 33
, compound, 34
, constant potential, shunt wound,
26
, differential wound, 33
, directions for starting and
stopping, '
definition of, i
starling and stopping, 36, 40
Ihree-pliase with controller.
"5.
Motor-controller, 125
Motor-generator, 9
, primary and secondary
windings, 9
, ratio of windings, 9
, object of, 33
potential circuit, 26
M
ACHINES, multipolar, object of.
Mean vatne of E.M.F. and cnr-
rent in alternators, 4
"Mesh" and "Star" methods of
polyphase transmission, advantages
and disadvantages of, g*
" Mesh " method of polyphase trans-
-' -■--,, g2
IS for ti
iways, ■
t potential (
, shunt wound, diagr:
constant potential circui
~ — , shunt wound, object of
inserting field-magnets in ci
, speed regulation of shunt, :
of
-, Ihree-phas
-, three-phas
■: 123
e-phas
upply, 99, 1
□n m spieed and torque, 44
Motors, compound wound, 82, 40
, asynchronous, 9, ro
, di-phase, 9, 10
-, gearleas, 68
— — , induction, 10
■ , polyphase, 10
, power of tramway, 67
, reduction of gearing of, 67
, reversal of single-phase, gS, 99
, reversal of three-phase, 98
, rotor circuits of, 112, 113
, stator windings, 112, 113
, starting of single-phase, 96, 97
, synchronous, disadvantages of,
9, 10
, three-phase, 10
, tri.phase, 8, 10
, two-phase, 8, 10
Multiphase. 4
Multipolar machines, object of, 2
Mutual induction, 8
in synchroniser, 87
„Gooi^lc
N°
O
HMlCn
Opposer, 83
Over-compouadiDg, objec
Overload switches, 78
PANEL, fault test, 127, 118
synchronising. 141, 1
Parallel, compound dynai
-, shuDt dyna
^.47
Paralleling, 138, 139
booster and cells, 160
of alternators. 87. 88, ill
of three-phase generators, 110
of two-phase generators, 109
Periodicity, 2
, advantages and disadvantages of
wide range, 3
, maximum and miniiunm, 3
, standard, 3
Periods, z
Peroxide of lead, 31
, colour of, 21
Phase difference, 76, 96, 97
, di, 4
, displacement of, 100
■'• i»iy-. 4
Qt, 95
relation of, 95
, voltage, 95
Phases aaxiliary, 96, 97, 9S, 99
, main, g6, 97, 98, 99
Phasing-up, 110
Pilot lamps, 107, io3
Plants, storage battery, boo
balancers, 76
and feeders, 77, 78, 79, 80, 81
Polarity, reversal of in booster, 86
Pole of dynamo, to find positive, 3
Poles, auxiliary, 39, 42
, commutatin^;, 39, 42
, compensating, 39, 42
Polyphase, 4
connections of rotary, converters
and transformers, 100, loi, 102,
ints, 89, 90, 91, 92, 93, 94, 95
for electric traction, iig, 120,
machinery ci
motors, advantages of, 92
six-phase methods, 102, 103, 104
. three-phase methods, 101, 102
two-phase methods, 100
transmission of power, 91, 92, 93,
94.93
, advantages and disadvan-
tages, 104, 105
, three and four wire, 106
, two- and three-phase, 106
.two-phase and three-phase,
with three, four, and six wires, 93,
94. 93
Positive pole of dynamo, to find, 21
Power, actual, 5
and lighting, by tow-tension three-
phase system, 106
, apparent, 5
— , to find, 3
Pressure regulation, on three- wire
system by balancers or equalisers.
Primary and secondary windings ol
synchroniser, 87
circtiit, 8
current. 8
m of, 112
/QUADRATURE, 4
R'
ACE of motor, 28
Railways, standard direct 1
pressures. 3
1 of speed of shunt motor.
)vGoo'^lc
i66 INi
Regalalor, induction, 105, 106
Regulators, field. 38, 39
. ; ahuQl, 38, 39
Resistance, non-inductive, 100
, " ohmic," 97
Retard or impede, self-inductance, 7
Reversible booster, g
, as arranged for traction
worlc, 85
for lighting work, 82, 83
for traction work, 84. 85, 86
— ., object of, and how attained,
83, 84, 83, 86
series motor, 40
Reversing cylinder, object of, 53
- — — barrel, 53
switch, 48, 52
Rheostatic brake, 58, 59
Rotary converter and transformer poly-
, three-phase methods, loi,
, two-phase methods, too
, six-phase methods, 102, 103,
converters, 9
and synchronous motors,
starting of, loS
and transformers for canal
haulage, no, in
on three-phase circuit, 114
— , practical working of, 114
, reversibility of, 114
, three-phase for electric trac-
tion, iig, 120
Rotor circuit, 10
circuits of motors, 112, 113
starter, 123, 124
and stalor, 10, 99, 100
Running-notch, 34
SELF-INDUCTION and capacity,
96. W
, effects of, 96, 97
— , effects of in held magnets,
*9
-, influence of, 7
Series dynamo, clockwise and counter-
clockwise rota lio
23,24
Series motor for tramways, 44
, maximum torque. 48
■ potential ci
, reversal of direction of rota-
Series, tramway motors in, 47
"Series-Parallel"' controller, 48, 49,
50.51.52.53,54
Brush, 59
, combinations effected
, connections of, 5a
, diagram of, 53
for electric vehicle, 66
. K.type, 53, 54
, saving by, 35
^_^ Thomson-Houston, 34
switch, 47
wound dynamo, description of,
Short-circuiting device for field magnet
coils, 29. 30
Shunt dynamo, clockwise rotation of
armature, 31
1 counter-clockwise rotation,
33
dynamos in parallel, 16, 17
— directions lor starting
and stopping same, 16, 17
motor, clockwise and counter-
clockwise rotation of arma-
ture, 32, 33
, speed regulation of, 28, 29
with auto starter, 36, 37, 38, 39
regulator, 38, 39
wound dynamos, 12
, description of, I2
— on constant potential
circuit, 15
-■ ■ -, starting and stopping,
directions for, 13
Single-phase, 4
alternators in parallel, 107
current supplyworkingthree-
phase motor, 99, 100
motors, starting of, 96, 97
, with auxiliary circuit,
96,97
, reversal of, g8, 99
pumping plant, 112, 113
, description of, 112
three-wire low-tension sys-
tem of distribution, 106
„Gooi^lc
Six-phase methods of polyphase rolary
"Slip!" II
allowed in practice, ii
rings, II, 89, 90
Sparkless breaking of circuit, 29
, conditions for, 29
Speed, constant, of motor shont wound,
z8, zg
36
regulation, shunt
, variable, of moto
Split transformer, 100
Standard direct curren .
for tramways, 3
for railways, 3
frequencies, 3
■ periodicity, 3
"Star" and "Delta" connection of
transformers, 107
and "Mesh" methods of trans-
mission, advantages and dis-
advanlaRes of, 92
method of polyphase transmission,
91
Starter^rotor. 123, 124
Starting and slopping dynamos in
parallel, 16, 17, 18, 19
, motors. 36—40
shunt- wound dynamo, 26, ij
of synchronous motors and rolary
converters, 108
Stationary motor, shunt wound, 26
" Stator " and " rotor," 10, 99, 100
" Stator" windings, 113
Step, phase or unison, SS
Storage batteries, 73, 76, 77, 78, 79, 80,
8r
battery, charging and discharging,
145, 146. 147
, discharge pressure, 71
with booster, 72, 145, 146
— — plants, descriptions of, 76,
77, 78, 79, So, 81
, variation of pressure, 70, 71
, working pressure, 71
Street car motors, gearless, 68
, power of, 67
n gearing of, 67
LS, alternating,
118
Swilcbboard connections, alternating
current at Hastings, 116, 117
Switches, "end-cell," charge and dis-
charge, 71
, object of, 70, 71
, horn break, 116
— , oil break, 112, 114
— , overload. 78
, underload, 79. 80
, water-break, 116, 117
Synchroniser, 11, 87, 88
. mntual induction in. 87
, object of, and method of using, 88
, principle of, 87
Synchronising generators, two- and
three-phase, 109, no. 144
lamps, 107, 108
, object of, 87. 88
Synchronous and asynchronous, 10
, advantages and disadvan-
tages of, 9, 10
— — and rotary converters, start-
ing of, loS
, disadvantages of, 9, 10, 11
TEST LAMPS, green and red, i
118
Testing polarity of dynamos, .
■ ■ tramway circuits, 132, 138
Three-phase, 4
, advantages of, 104, 105
— adjustable choking coils. 113
1 function of, 116
circuit with rotary converters,
— — currents, possibilities of, 104
distribution for power and light
tng " Star" method, 104, 105
, disadvantages of two-phase, 104,
— circuits, go
— methods of polyphase rotary ci
verier and transformers, i
supply, 99, 100
— rotary converters for electric tr
)vGoo'^lc
Tbree-pbase switchboard circuit,
137
system, low-tension, 106
, for power and lighting, 106
transformers, 110, iii, 120. 121
for electric traction, no,
transmissioD, Star and Mesh, 94,
95
with three, four, and siji
wires. 94, 95
Three-wire system, regulation of pres-
sure 73. 74
— — with balancer, 73, 74
■ — ~ — and batteries. 65, 75
with batteries and booslers,
. l^- " ,.
— _ with equalisers, 73, 74
Traction switchboard, 129
Tramway circuit, 44, 45
, series motors on, 46, 47
. in parallel, 47
— - motor, advantages of, 36
, series, 36
, torque and speed, 36
motors, gearless, 68
, power of, 67
— , reduction gearing of, 67
, speed acceleration, 50
Tramways, standard direct current
pressures, 3
Transformation, ratio of, S
Transformer and rotary converter poly-
phase coimeclions, 100,101,102,
, six-phase methods, loj, 103, 104
, three-phase methods, loi, 102
- — , two-phase methods, 100
, discriminating, 118, 119
, description of, 119
, object of, 119
, split, 100
Transformers, 8
, stepi-up, 8
, step down, 8
Transformers and rotary converters for
canal haulage, no, in
, primariesconnecled" Delta," 107
, secondaries connected "Star,"
IQ7
, three-phase, no. Ill
Transmission, polyphase, two- phase,
and three-phase, 93, 94
Tri phase, 4, 10
Two-phase, 4, 10
generators, paralleling of, log
, collecting currents, 89
methods of polyphase rotary con-
verters and transformers, 100
transmission, 105
, disadvantages of, 105
with three and four wires, 93
U
NDERLOAD switches, 79, 80
, ingenious, 80
Unison, step or phase, 88
VAIilABLE speed motor, 27, 28
, reasons of, 27. 28
" Virtual " volts and amperes, 5
Voltmeter method, testing polarity of
dynamos, 20, 21
Volts, virtual, 5
■yy/INDINGS, inductive drop in.
Wiring connections, 63
diagram, 63, 64, 65
of cars. Brush system, 60
of controllers. Brush, 59
diagram of Brush controller, 6z
primary and secondary oi syn-
chroniser, 87
IW, A'C ft' L».| miff TEIl» LOI
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